Is there a reason to believe this is how things work? Rather than "within a democracy as long as 'trans rights' means something that most people disagree with, it will be harder to advance the pro- side of the issue"? Is there evidence of 'momentum' being a real thing in politics, as opposed to the 'pendulum' that I've witnessed over the last decade?
If you go back 15 years or so, you hear the exact same "concerns" about gay people pretty much word for word. Now that they're no longer an acceptable target for most people, they've moved on to regurgitating the same baseless fear mongering but targeted towards trans people. If society manages to progress further, they'll eventually come up with another group to serve as the "other" that they can blame everything on.
Everything related to the right wing and fox news? We never had a big "swing left" - clinton was the democrats showing they can do economic conservatism as well. Modern acceptance of trans folks isn't a pendulum, most of the people espousing anti-trans views weren't pro trans 5 years ago.
Trying to abstract history into major shifts that are attributable to inanimate objects is just very ludic fallacy.