They were sick of Republicans getting battered by the media and their opponents. Every time the Republicans put up a "nice guy" the media skewered them along with their Democratic opponent. Think Bob Dole, John McCain, Mitt Romney. All decent guys, completely dismantled by their opponents and the media and turned into evil men during their campaigns.
My friends voted for Trump because he was a straight up brawler. The guy didn't back down, he didn't apologize, and was a flame thrower.
Clinton tried and tried to go after him and everything fell flat. He went after her, labeled her "crooked Hilary" which his base ate up. He talked about her husband being a rapist and how she allowed it and they went nuts about that. Nothing was off the table and it kept her completely off balance, she had no comebacks for most of his attacks.
The media went after him and what happened? He punched back - repeatedly and they were unprepared for him. Called him a joke, derided him, tried to bring him down. He just kept coming back and countered with something they weren't reporting on, or the polls being way off, or any other number of issues. The media were so unprepared to deal with him, even more so now that he's been elected. In one election, he completely dismantled the MSM and convinced half the country they couldn't be trusted. How many times a day do you hear the term "fake news" now? Trump started that. Now the media can't get away from it and now it's a part of our political lexicon. CNN is no longer a reputable news organization because Trump called them out repeatedly, their reputation is in tatters because of him.
The Republican base ate him up and loved the fact they finally had a candidate who played in the mud and never tried to be the "nice guy" and fought the media and Democrats with everything he had. It's not that they knew what they were getting, it was more about pushing back the Liberal ideology, and feeling like they had someone who would fight for them.