Okay. Okay okay okayokayokay
But Aziraphale isn't a fool.
If there's one thing that was made very clear in the book, it's that Azirphale - for all his naivety and pointless hope in a broken system - isn't a fool.
The way he looked back at Crowley, the way he clearly immediately wanted to go tell him, the way we got to *watch* Aziraphale lock himself away on the ride up that elevator.
I don't think he was going to go. Not really. Not until Metatron said, "Second coming."
Aziraphale isn't a fool. Aziraphale knows that the second coming is the precursor to Revelation. Which is just another word for "the extremely gory, firey deconstruction of the planet earth according to biblical prophesy."
Because Crowley was right about something more important than the two of them loving each other; the real one - the Big One - is coming.