Timespan in tv shows always feels shorter than the actual story, because of obvious reasons, the fact is Dean and Benny had been searching for Cas for weeks, maybe months, so Benny was probably already suspecting Dean to be in love with his Angel, but seeing them together definitely confirmed his belief.
Benny knew at this point, he knew that Dean would be destroyed if he lost Cas, so he saved Cas for Dean, he did it for Dean, and I can’t help but make the parallel with 12.12 when Crowley saved Cas, for Dean, and I feel sorry for Crowley and Benny, and I even wonder if they didn’t sacrifice themeselves because they knew that their love for Dean will forever remain unrequited because Dean already gave his heart to the Angel in trencoat.
Ah Spn , you can be so beautiful and romantic when you want too. I miss this Spn and i miss S8 so much it hurts.