Super response, Irene. Still, don’t conflate today’s GOP with the traditional Republican Party. That ship has sailed. Republicans made a pact with the Devil many moons ago when it became obvious that demographics were running against them. They simply dog whistled the xenophobic crowd to make up their voter deficit, and so by the time that Trump came into the picture the know-nothings owned the party. Hell half the once good Republicans are now on MSNBC. Guys like Steve Schmidt could teach the Democrats a good lessen.
So when you say they should have slammed the breaks on Trump early, they did’t have anywhere close to the numbers needed to pull that off. Trump waited till just the right time to jump on a revised GOP. There is in effect no Republican Party, just a bunch of mindless Trump reality TV fans who think government can be good entertainment. They know not what they play with, but as you can see Putin and the Russians do.