It was never one thing. The GOP had 8 years to craft a strategy against HRC. They knew she would be running after Obama and keeping the negative spot light on her was second only to discrediting the Obama administration. Clinton was no "shittier" than any other politician, so the only way for the GOP to win was to indict politicians as a whole. This lead to Trumps win and even thought it was not the way they wanted it, they were more than willing to jump on the bandwagon.