I don’t see the issue. If the Republican party dies conservatives will just flock to a new party. It doesn’t happen very often in the US but such things have happened.
Republicans were too accepting of extremists in order to win short term gains. Now they’re paying the price as moderates leave the party, making it even more extreme and unredeemable.
They embraced an authoritarian and just like every authoritarian he won’t stand for criticism. Anyone that doesn’t support the authoritarian is out.
If conservatives really want to have a political future they need to abandon the Republican party and make something new. Something that isn’t extremist. The problem with making that happen is they’re coming to find out that even their most fundamental beliefs–the things that make them conservatives–are what everyone else thinks of as extreme.