MAGA is not interested in building anything, in winning a real majority, in constructing an actual future rather than lamenting an invented past. Everything is performative and destructive. It’s all driven by who they are against rather than what they are for. As a Republican Senator told Romney as he settled in, their view is that the first consideration in voting on any bill should always be: “Will this help me win re-election?”
There’s no definitive moment in the collapse of a republic, but that quote comes close. If all you care about is your own grip on power, regard the opposing party as ipso facto illegitimate, and give zero fucks for the system as a whole, a liberal democracy has effectively ceased to exist. A single major party, captured by radicals and nihilists, can do that.