He's an idiot for doing this.
But then these days, it seems like everyone's an idiot. Demons who think the devil loves them. Angels who think the battle will be just like tearing off a band-aid. And humans... well, if they're all as slow-witted as those brothers, then it's no wonder the shit has hit the proverbial.
So in a way, it figures. He's surrounded by idiots, might as well become one.
Guess the Apocalypse has a fifth horse. Sheer stupidity.
Because how else could it be that while he should be looking for mythical planes of existence to avoid being destroyed, instead he's nuzzling a fallen angel's stomach, licking up to her sternum, waiting for that smile of delight to crawl across her face. That wicked, wicked smile. And then he listens for the sounds that spill out of her mouth as he kisses downward, inward.
He knows that if Anna could help some human or angel by killing him, she will. Lover or not, they're a demon and an angel, and she could outpower him any day of the week. He knows that yielding to this temptation is stupid. Stupid, stupid, stupid.
Literally, apocalyptically stupid.
Yielding to the temptation of Anna's body, Anna's perfect wicked smile, Anna's wings that sting him with every flutter-light touch: it's stupid. But the pleasures of the flesh are one of the finest things about this earth, with its orchards heavy with plump red fruit, its dirty caves full of gleaming jewels.
And this earth - and its pleasures- might well have an expiration date, it seems.
So Crowley is willing to yield to temptation. And to yield, as always, to his own stupidity.