It's really not about them "believing" it. They tend to "believe" any new reality they are presented with if given by the "right" person. And they will just as quickly discard those "beliefs" if they are told something different by the "right" person. Trump is that person for them right now. Ultimately there is no value that "conservatives" aren't willing to abandon other than maintaining the hierarchy. Everything else seems to be in service to that end. They fight hardest when new groups are receiving rights they didn't previously enjoy. It's never been about "fiscal responsibility". It's never been about "small government" or "states rights". They are quite happy to abandon all of those if a trans person might be be able to use a bathroom in peace.

"When someone shows you who they are, believe them the first time." ~ Maya Angelou