It being immediately post-Obama and Trump being the only candidate willing to be insanely overly racist basically sealed him in as the Republican candidate. There is a large portion of white America that could not cope with a black man being president, much less for two terms. They had basically a decade where they were getting more and more riled up by every right wing talk show can you can imagine. Satan himself would have been elected if he dropped a hard R n-bomb on TV.