Heh dont get me wrong. I think Obama is a philosopher king but by giving such emotional speeches and rhetorics he set the stage for very strong reactions. Reactions that bloomed into the awful culture wars of today. At the time I saw Obama as a good politician but the wrong time for it. Mitt Romney was a good candidate that would likely have normalised the tensions post 9/11. Alas it did not happen so.

The current republican candidate is highly different. He fomented a mob on the steps of the capital because he was upset he didn’t win.

The others you mention just had political qualities people disliked.

That's part of the point. People spewed vitriol at both Bush and Trump with similar levels of hate. It didn't matter that they were of different quality.

If you're already 100% sure the other side is going to passionately hate your candidate, no matter who you pick, then you can't win by choosing a reasonable or moderate candidate. Therefore, you pick whoever has the strongest appeal amongst your side.