> What trigger are they waiting for, exactly?
Critical mass.
Look, I could pick up a rifle tomorrow, and march on DC by myself with the intention of toppling the fascist regime. And what would result? I'd be quickly arrested or killed and nothing would change. So what's the point?
But if I was part of a group of 1,000,000 like-minded people, then I might still be arrested or killed, but at least there's a much higher likelihood that some actual change would take place.
Now, as a lifelong believer in the "an armed populace is to protect us from authoritarian government" mindset myself, I have to say, I am extremely disappointed in a lot of people right now. People that I grew up with, that I've always trusted, respected, and maybe even admired. Because while fascism metastasizes and spreads through our country nearly completely unchecked, they all seem unwilling to even speak up against what's going on. And I can't defend their choices, but I can say that I still believe that there is a tipping point, some event, or sequence of events, that would kick things into into gear if needed[1].
[1]: I say "if needed" because it's not 100% clear to me that the only possible way out of this mess is an armed uprising. We might still be able to "vote our way out of this" and the optimistic take is that many Americans are sitting on their hands as long as they hold a shred of hope that that is still possible.
The more pessimistic take is that a majority of the "second amendment to protect us from authoritarianism" crowd are hypocritical ass-clowns, who are actually OK with authoritarianism as long as "their guy" is the one in power. :-(