I don’t think the likes of Boebert or Greene would have been viable candidates in 2012. While the Tea Party caught the Republican establishment by surprise, they at least made an effort to reign them in. I don’t think the Republicans of 2012 would have allowed Greene to serve on a committee given the behavior she’s demonstrated. No candidate in 2012 would have been able to mock McCain for being a POW like Trump did in 2016.
I must point out that the Republicans have been doing this long before Trump. You’re right on about everything else, but I think this was a Gingrich thing.