Good Omens S2 Episode 6 confession scene speculation:
Aziraphale didn't respond to the love confession from Crowley because he didn't realise it was one until Crowley mentioned the Nightingale and kissed him.
Allow me to explain.
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Aziraphale interrupted Crowley to give him the news from Metatron, so when Crowley starts his spiel:
"We've been together a long time, I could always rely on you...we're a group....we've spent our existence pretending we aren't...if Gabriel and Beelzebub can go off together then we can...we don't need heaven/hell they're toxic...you and me whatya say?"
Aziraphale interprets everything Crowley is saying as his rebuttal to the 'good news', not a separate declaration of his feelings.
What Aziraphale just told him shaped Crowley's confession, instead of finally telling Aziraphale how he feels about him, he's now backed into a corner and trying to change Aziraphales mind. Offering to run off with him as the alternative to the Metatron's offer.
The repetition of the phrase: "go off together" from the bandstand fight in season one feels very intentional here. It would be easy for Aziraphale to think 'this is just Crowley's response when the divine plan interferes, he always wants to run away'.
Aziraphale believes that he just needs to make Crowley understand the situation and opportunity that this is and everything will be alright:
"Come with me! To heaven, I can run it, you can be my second in command. We can make a difference!"
Crowley is looking defeated already, in his mind he's bared his soul and Aziraphale is a brick wall. So if he can't tempt the angel into staying with the love he has for him (which Crowley thinks he's declared but he really hasn't), he'll get him to change his mind by evoking something else he loves:
"You can't leave this bookshop."
Aziraphale scoffs fondly. 'Silly demon, you were just suggesting we run off together and abandon it only a moment ago!' He thinks Crowley is trying to 'work' him here and the old serpent might even be selflessly trying to spare the angel the loss of his beloved bookshop in order to restore Crowley and help the world, which would be just like him to be so covertly protective. So Aziraphale reassures him, a bookshop doesn't matter to him as much as Crowley and the world. It's just a collection of objects really. Humanity is more important. Crowley is far more important.
"Oh Crowley, nothing lasts forever."
Crowley is crushed. Nothing lasts forever. Not even the two of them. So he covers his sadness with his glasses, walls back up, and he tries to leave.
Aziraphale is baffled. He just reassured Crowley that he was alright with change if it means things could be better. Why is Crowley leaving? Is he worried that they won't spend time together anymore? That he won't have time for his friend as a supreme archangel?
"Crowley come back!....we can be together, angels!...I need you!"
Crowley can't even look at him in that moment. Why would Aziraphale say that? The two of them together only if he accepts heaven again? Conditional love? That's not fair. It hurts.
Aziraphale meanwhile is hurt by Crowley's turning away, his silence and a bit incensed at what he perceives as ingratitude. Aziraphale didn't really want to go back to heaven, but he'd do it if it meant Crowley could be happy and safe and Crowley doesn't seem to appreciate that:
"I don't think you understand what I'm offering you."
Crowley went through the fall. He asked the questions. Did his best to protect humanity and it has brought him nothing but suffering. He's well aware what's on offer. He's seen heavens cruelty and capriciousness firsthand and been burned by it repeatedly. How can Aziraphale choose them over him and still think everything will work out?
"I understand. I think I understand a whole lot better than you do."
Crowley loves Aziraphale's big foolish optimism and kind heart and he thinks it's the very thing taking the angel away from him. This isn't how it was supposed to go. It's all slipping away from him.
"Listen. You hear that?"
Aziraphale can't even keep up at this point.
This is what comes of thousands of years of 'not talking about it' and living under threat of holy retribution if they are discovered. They're talking past each other, having two different conversations. Obfuscation and code has become their communication medium by necessity and it's failing them.
It's frustrating Aziraphale that he can't get a grip on this conversation:
"I don't hear anything!"
And Crowley drops the bomb.
"That's the point. No Nightingale's."
Oh. Suddenly we're on the same page. You can see from Aziraphale's face that he understands to what Crowley's referring. The Nightingale in Berkely square. Angels dining at the Ritz...
"You idiot! We could have been... us."
Crowley's talking about the big unspoken thing between them. Their relationship, thousands of years of dancing around each other like binary stars gravitationally and inexorably drawn together over and over. The thing Aziraphale was beginning to be bold about, (dancing notwithstanding) before Metatron came along and distracted him.
And it seems to Aziraphale that gut-wrenchingly, Crowley is finally acknowledging their mutual love only to point out that it's gone. Lost. They could have finally been together, an us, but Aziraphale ruined it because he's an 'idiot'.
After being quietly in love with Crowley for years, for Aziraphale to have his offer to return to heaven together and his unspoken love rejected in one fell swoop is devastating.
Overcome, he begins to cry and turns away, not wanting Crowley to see how hurt he is.
Crowley for his part is desperate. He has to do something. Maybe Aziraphale doesn't understand what Crowley is offering him! One fabulous kiss and va-voom right?
In a final desperate act, he kisses Aziraphale. Tries for passionate. Tries to show him that he loves him and show him what they could be because his words clearly aren't working.
Aziraphale is shocked and angry. He wants to kiss Crowley of course. But not like this. Not as a taunt. Crowley just told him their chance is over so what else could this be but a final insult. A kiss to punish the angel. It's a cruelty he didn't believe Crowley capable of.
And despite how mean it is. It's also what Aziraphale has wanted for so long he can't help but melt into it for a brief moment. Allow himself to feel what it would have been like to be that close before losing it forever.
Then Crowley lets go and Aziraphale breaks away on a sob, feeling wounded. Hurt beyond words that Crowley would use his feelings against him like this, gutted to be losing the man he loves and not understanding why.
The worst part is that Aziraphale doesn't have it in him to hate Crowley, even if he thinks the kiss was a cruel gesture. He still loves him. So he gathers himself and does what Aziraphale does when someone hurts him.
He forgives.
"I forgive you."
I forgive you for rejecting my attempt to restore you and make you happy, I forgive you for rejecting God and heaven yet again, I forgive you for acknowledging our love and then rejecting it. I forgive you for kissing me, giving me a fleeting glimpse of what we could have been to each other. I love you and I forgive you all that.
Crowley is done. Breath knocked out of him on a last sigh. He tried. And the Angel forgave him yet again for something he never asked or wanted forgiveness for. He doesn't want to be penitent for loving Aziraphale. Shouldn't have to apologise or regret wanting them to be together.
"Don't bother."
Aziraphale looks surprised Crowley is leaving because he genuinely is. He can't understand how it's all gone so horribly wrong. He gasps, shocked and can't even call out to him to stop, come back.
He cries, touches his lips where Crowley had kissed him. Tries to gather himself and barely has 10 seconds before Metatron is back.
At the end of that scene:
Crowley thinks he confessed his love and Aziraphale chose heaven over him because he didn't want to stop being a demon.
Aziraphale thinks Crowley rejected heaven, then rejected Aziraphale and threw their love back in his face as a final unkindness.
Aziraphale leaves and goes to heaven anyway because in his mind he's already lost Crowley and there is nothing left to stay for. If he doesn't have Crowley he needs a new purpose and it's going to be saving the world. He'll convince himself of it. And he'll push that broken heart down and the pain will fade if he just smiles through it. It will be enough, to make heaven better. It has to be. Maybe if he proves that he can make a difference Crowley might see the error of his ways and speak to him again? Surely. Hopefully.
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Both of them are hurt and confused and lost and oh dear hell I really feel for them.
This is what I've thought from the very beginning. I do not think Aziraphale realized what Crowley was telling him anymore than vice versa. "Let's run away together"? That's not a love confession. He's HEARD that before, and it didn't go anywhere, despite the fact that he's been virtually throwing himself at Crowley for the past four years.