In short? Because we were (foolishly) convinced by a message of small government, but also respect for and protection of individual rights, that a regulated capitalist system provides broad benefit to all classes, etc. (seriously, just laying out broad strokes). And I DO believe that regulated capitalism does that -- it does so elsewhere, it's just that now, MAGA calls that approach "SOCIALISM!" If you want to make it even shorter....read some issues of The Economist for a basic center-right perspective. Most of us still agree with much of that. But realize that "center-right" actually INCLUDES things like some form of universal health care, actual regulations on capitalism, and being in favor of managed and reasonably regulated global trade. Today, MAGA literally calls The Economist a "leftist rag." So, we're Economist readers. For a long time, the American Republican party generally aligned (at least in its messaging) with the values and approaches voiced there, so it made sense for us to find a political home there.
Did the Republican party ALWAYS have these flaws running through it? Of course it did. We're also pragmatic in knowing that all parties/movements have flaws. But now we live in a world where the GQP has given in to every last one of its worst impulses.