This doesn't match the experience I have when I try talking to people who are anti-trans. They don't argue that people using the wrong bathroom was always a threat and that they're more aware of it now. They argue as if it's a new problem. So in my opinion awareness is not a good enough explanation on its own to describe why they're talking about the issue now.
Boy and girl sports leagues reinforce this conclusion for me. I'm watching people who I know have never once argued about the integrity of girls' sports in any capacity suddenly tell me that this is a pressing issue that is reducing safe spaces for women. It's hard to explain that shift without tribalism. Maybe it's just ignorance of what's going on, maybe they don't actually realize that trans athletes aren't a brand new thing, maybe they believe this is a novel situation. Or maybe some of this is fueled by reactionary rhetoric from leaders and new sources, both of which really shouldn't be able to believably claim ignorance as an excuse.
It's not universal, I don't claim that tribalism explains everything. But you can at least in theory point to environmental issues and argue about them using actual data in the real world. We can point to statistics about, say, incarceration and show that it was a problem before awareness went up. We can point to environmental issues and believably say, "species were always going extinct and we would like it to stop." In contrast, there's no objective reason to argue that transgender athletes are more dangerous today than they would have been in the past. And importantly, there's very little to point to as evidence that anybody was getting hurt because of transgender athletes in the past. It's not just a 1st-world problem that people suddenly have bandwidth to argue about, it's a debate that's almost entirely defined by opposition to a social trend rather any kind of data or visible problem.
I do think at some point it makes sense to call that a reactionary movement.
And of course, this isn't necessarily Republican-exclusive, I do also see Democrats who call themselves allies but have done very little research about what problems trans people face or how trans communities talk about these issues. And I do think there's a little bit of tribalism there where a subset of the Democratic party has picked a side in this debate based pretty much entirely on their party identity, not because they understand what's going on or because they've done any research. However, in my opinion there's comparatively very little real-world harm from clueless allies, so I spend more time focusing on the Republican side because laws that restrict medical care for children are just obviously a more harmful, dangerous result for the trans community than a tone-deaf message from a company or a poorly phrased Facebook post is.