In essence, the left fucked up on this issue by letting the super-progs dictate its terms. And with that group, there's no cause too small that it can't be treated like the most important thing on Earth that everyone needs to get behind or they're bad, bad people. While they self-sabotage their efforts every step of the way with their "If you aren't cool with everything, FUCK YOU!!!!!!" attitudes. AKA: The same sort of thing we're getting now with certain Ds or D-leaning TV mouthpieces playing the "we only lost because this/these demographic(s) are TOO STUPID to do what they should have!!!" card.
I mean, just the concept that a group that's as small and insignificant in the grand scheme of things as trans people was so prevalent in election ads and a focus point of the campaigns of Trump and other prominent R candidates is insane. But the left just sort of skipped the "tolerate" and "accept" stages and went right to "celebrate" and did so in ways a lot of people didn't like, such as the "born male, competes with females" stuff and the Rs kept up their proven track record in amplifying and exaggerating things, setting up a situation where a lot of people probably were swayed towards the right by that issue -- at least far more than would be swayed left by it.
Seems like this wouldn't have been much of an actual issue if trans advocates were more like, "Trans people are people, too; live and let live; be cool" and left it at that. But that doesn't make the over-the-top advocates feel like they're doing their job, so that didn't happen, we got a world where a certain portion of the population feels you committed a hate crime if you "deadname" the wrong person and that just didn't resonate all that well.