Your theory is probably correct, and it is properly seen as a suicide pact.
What the current conservatives are doing is painting themselves into an ever-smaller corner. They may be the “purest” conservatives around, but their deeds are so odious that even former supporters are moving away from them. So they’ll ultimately end up as small sect, sort of like Jill Stein and Gary Johnson in 2016, who had a small following and ended up baying at the moon.
But there’s a more fundamental issue to talk about -do these people (who call them conservatives) really stand for anything at all? Or are they nihilists and destructionists who don’t have an agenda other than to destroy? That’s worrisome.
Somewhere the multi-party system in the US has to accommodate a middle-of-the-road conservatism (think: Nelson Rockefeller, William Weld, John Anderson, John Lindsay), If the republicans don’t embrace moderates then over time, they’ll move to become democrats.
So based on your theory, the republican party is killing itself. It may take another ten years, but it’s inevitable if they continue on this path.