The most famous forms of Holocaust denial and revisionism tend to focus on Jews, casting doubt, for example, on how many were exterminated in the camps. But denying the impact the Nazis had on the other groups they targeted, including queer and trans people, disabled people and Romani people, is still Holocaust denial. Maybe someone should tell J.K. Rowling.
I think the trans thing started as a sincerely held conviction very much a long the lines as you’re describing, and while this is and can only be utter speculation, I have a feeling a lot of what comes after as in Chappelle, probably with Linehan (but I don’t really know anything about his case) and also other examples like the vaccines cause autism guy, I think these people are seeing an opportunity in their ostracism to keeping their profiles high and business opportunities as well.
I think it’s a sort of a ‘hung for a sheep as for a lamb’ kind of logic where you mightn’t really have had any particular common cause with a lot of conservative views, or fringe elements before, but their willingness to embrace and lionize you for this one particular stance creates a new audience and market for you just as others are shrinking. From there it makes sense to gradually dole out hints and allusions to more conservative talking points and just keep ratcheting it up piecemeal to keep that profile up. For this to work you have to eventually be less hinting and more direct and the positions have to be more extreme and on more and more diverse matters, even ones you probably never had any opinion on because this is a pathway to becoming a kind professional provocateur and shock jock.