Well, since you're talking about the Republicans during Obama's terms: how did that happen in the first place? I mean, if democrats are so great and all, why did the Republicans take over the Senate and the House? That's something I'd like to know. The reason would likely be the same as why people chose Trump over Clinton (not by popular vote though, but still).
By the way, there's also democrats who support some of Trump's ideas (Sanders for example, supported his decision to opt out of TPP), so there's that.