Trembling like a little wet idiot again because BECAUSE
Eve was tempted to take a bite from the apple. The Original Sin! It separated her and Adam from God. They were banished from Eden, they had to leave God's Safe Garden, and, for better or for worse, had to venture out into the broader outside world
Diavolo planted a fucking apple orchard for Lucifer while Lucifer was still an angel, just because Lucifer offhandedly mentioned liking apples. It was a gesture that was probably one of the stepping stones towards their budding friendship and towards Lucifer questioning the celestial realm and his father, towards Lucifer's growing anger. One of the many* contributing factors towards Lucifer starting a war against the Celestial Realm that would eventually get him and his brothers banished, that would force them to leave their Father's Safe Realm, and, for better or for worse, venture out into the broader outside world. That would cast them into officially becoming Sins.
And Nightbringer has so much apple symbolism relating to Lucifer, that it's on the fucking title screen itself** and up until the present moment Lucifer's favourite food is Poison Apples (it's not even on the nose anymore, it's just straight up a punch to the face)
Diavolo may not have meant for it to be as such, Diavolo 100% only did it because he was starry eyed over Lucifer from day 1, but at the end of the day a Temptation is a Temptation and he held out the Apple and Lucifer took a bite
*the main reason was obviously Lilith, which y'know you could kinda lowkey parallel with some of the stories about og! Lilith's part in the whole apple/eden thing
**and it's explicitly stated that the type of apples Diavolo grows are a deep, vibrant red as opposed to Celestial Realm apples which are all gold & shining:
