Yes, it's absurd, but it happened. Even many Bernie bros got sucked into the manosphere & went down the alt-right pipeline. Latino & black men voted for Trump in record numbers. Some for economy & many for culture war issues. Not just trans, but grooming kids & drag queens. Muslims also.
There's an article in TNR (I'm having trouble linking it) from about a month ago called "How Rahm Emanuel Got Trapped In The Bathroom" that deals with this phenomenon. The gist is that this was a Republican-manufactured issue, and the dems just tumbled into their frame.
And why wouldn't they? Every single time a Pub stokes up irrational fear of whomever they are focused on hating this round, they accuse the Dems of being soft on [insert dogwhistle like law & order, crime, terrorism] and the Dems ALWAYS try to pass the unpassable purity test to our detriment
Also, the dems have a bad habit of letting the GOP define the terms of the discussion, resulting in them always reacting, always playing defense, always feeling that they need to throw someone under the bus to appease the unappeasable. There are plenty of ways to go on the attack. Dems seldom do.
But ultimately the blame falls on the voters for letting themselves get manipulated by this crap.
Dems desperately need a (left-wing) media apparatus like GOP has. All of the right (from alt-right white nationalists to evangelicals to podcast bros) may disagree but will unite behind Trump to win elections & yield power. The left are splintered groups of "Dems are bad," infighting, & purity tests
Is it? If you vote for a guy that tells you he's a progressive, you expect him to be a progressive as he literally promised on his campaign trail. And that's before we get to ES&S systems, decades worth of gerrymandering (that white folks just noticed), dark money, and hanging chads.