Why Republicans claim they were radicalized
By 
Seth Masket on Ben Shapiro explaining that he and many others went full MAGA because Obama made some anodyne comments about race during his presidency:
This is an important narrative, and it’s not a position just held by Shapiro. Quite a few conservative authors make a similar argument, and I’ve heard similar sentiments from some local political figures I’ve interviewed. The basic idea was that there was some sort of deal: If conservatives permit the election of the first Black president, that will essentially signal the end of institutional racism in the United States, and then we won’t have to talk about race anymore. And any time Obama brought up race he was reneging on that deal.
Now, that narratives breaks down somewhat in a few key areas, such as the fact that this “deal” only existed in conservatives’ minds, and they didn’t vote for Obama anyway. Also, MLK’s dream was about equality and justice, not about putting a Black man in the White House. But Obama, in his style of campaigning in 2007 and 2008, surely did a fair amount to suggest a “post-racial” United States, and sought to allay conservative whites’ fears that he would mainly prioritize Black voters.
My own perspective and Shapiro’s perspective on the past several decades of US politics clearly differ, but there’s a common thread in that racial politics is the main driver. Klein’s question about the Gates beer summit — “That’s what radicalized you all?” — is the right one, and the answer is yes. But it was always about more than a beer summit.
The other, related “deal” that existed in the minds of elite Republicans was that when a non-lunatic (barely) won the 2012 primaries (despite effectively running unopposed) that meant that Democrats were obligated to let him win, and therefore Obama running a completely standard-issue presidential campaign was an unforgivable attack on civil discourse in America.
This is another way of saying, of course, that Trump or someone like Trump was eventually going to lead the Republican Party irrespective of what Democrats did.