Why?
It happened when the evangelical Christians got hold of the party 10 years ago. Well intended, but still paying for the split.
I think it better to beat the she-at out of the RINO's internally rather than in public.
I understand what you are saying. I think the answer is really one of leadership. Reagan was able to build a grand coalition. HW sort of blew it. W rebuilt it, and is now squandering it by being a weak leader. Which is surprising because his main appeal to me originally was that he was a strong leader.
The various factions of GOPers are held together by strong leadership that proposed bold initiatives regarding our shared goals.