People cross-dress for a lot of different reasons. Some are entertainers. Some do it because their mind doesn’t match the body they were born with. Some do it to attract a member of the opposite sex (opposite to what they look like when they’re cross-dressed, that is). And for some people it’s just a really, really terribly exciting thing to do; a rush like no other. You don’t have to guess where on that spectrum your author can be found—you can read about it right here! Happy, happy, joy, joy!
The only caption I could find that involves a guy becoming a womanly bride is “Bride to Be” from 2015. There could be others, but then again maybe I just haven’t written enough boy-to-bride caps. I’ll try to fix that.