Okay, so when Bush was president early on, I think the support from republican voters was acceptable on some intellectual level. After all, compared to Trump, Bush was mature, professional, and had a sense of dignity. It would be easy to over look his bad decisions as president within his first few months.
Trump is something remarkably different from Bush. The American people somehow managed to elect someone even dumber than Bush and not only is Trump very dumb; he has the emotional maturity of an 8th grader. This is a guy who went on 3AM Twitter tantrum because a beauty queen said something mean about him. The leftwing was bewildered when Trump became the republican nominee. How could they not? Bush at least developed psychosocial skills that an adult his age would normally have. Somehow, the standards of republican voters' devolved. Is it that Republican voters themselves devolved?
Was Bush simply the start of a new trend? After all, Reagan would be a liberal by today's standards based on the policies he pushed.
Are these voters so stupid that they chose Bush and Trump as their nominees simply because they could understand what they were saying? See, when Bush spoke during 2000 campaign season, republican voters probably thought "Okay, i understand most of what he is saying but not all. I guess that's good enough. He talks about lower taxes and that's all I need to hear really!"
Then their savior Trump came along. The man who talks like a 9-year-old and comes up with policy ideas just as simple. Republican voters thought "I understand everything he is saying! Finally, someone gets me! Wait, he wants to build a wall? I have one of those at home! Trump gets me! He has my vote!"
Now, how the teabagger movement fits into all of this is another subject, but what's apparent about that movement is that the corporate masters behind the scenes could easily manipulate the republican voter to support their agenda regardless of how much it goes against the republican voters' interests. Trickle down economic theory sounds like a good idea, so voters just went with it even though it's been proven to be complete bullshit. Bush and Trump merely facilitated this cult-like behavior more efficiently.