I believe Donald Trump was elected because of a culmination of several different ideas and attitudes. I grew up largely in the South, and in conservative communities, so I experienced these attitudes first-hand. Below are as many of those ideas and attitudes as I can identify, written in the best words I can find to express the idea(s). I even have personally identified with some of these attitudes in my youth, but definitely not any more.
One important note: if anyone in the future ever quotes me as "saying" the things below, without putting them in the proper context (what I said in the above paragraph), I want to be clear now that I will consider trying to put the below words into my mouth (which I either never agreed with, or have not agreed with since I grew up and matured), to be defamatory action against me. Please don't do it.

Here are as many of the ideas and attitudes that I believe came together to allow Donald Trump to become president:

1. You can't tell me what I can and can't believe or what I can and can't like, or tell me what to think.
2. I grew up happy and proud of my (conservative/white) heritage, but now I keep hearing the message that I should be ashamed of it. This is one of the reasons I don't like politics. I feel attacked, and voting for Trump is one of the most powerful ways to fight back that I've come across in decades.
3. A huge part of politics deals with making sure that people are treated fairly. To me, this means making sure that I, (and people like me), are treated fairly. I might not be as preoccupied with making sure that "my people" are treated fairly if I already felt like this was the case, but it's not. I see so many people actively engaged in making sure that other groups of people receive special treatment long before I do, that I feel like I will be forgotten if I just sit back and don't advocate for myself in day-to-day life (and if I don't elect people who will similarly advocate for me in government). If I already felt like I was a member of a group of people who receive preferential treatment, maybe I could be more generous about groups I don't belong to also being treated fairly, but that's so far from my reality, that the idea that I actually get preferential treatment makes me laugh. In my opinion, any theoretical lack of negative treatment (something  as far from "tangible" as anything that anyone could ever be asked to identify with) never makes up for the positive favoritism that I see others receive. The only way I could truly understand the daily reality of people who experience systematic prejudice would be to listen to people who have experienced it. A lot. Like for years on end. Who wants to do that? I avoid negativity, because it brings me down. Furthermore, not having to think about the crap others must deal with day after day is a privilege of being who I am. See #1.
4. Because of #2 and #3, I don't like politics in general (there is nothing positive in it for people like me, only negatives). Politics is nothing than people squabbling over who has the worst life, and trying to get other people to do something compensate for that. People just need to live their lives and get along, without having to try to get the government to make up for their bad luck or bad choices.
5. Politics is a necessary evil. And like other necessary evils, we can pay other people to deal with it so we don't have to. Politicians who are not white are almost always people elected and paid to try to screw me over. White, liberal politicians can't even be loyal to their own people, so screw them. And even white, conservative politicians too often have to make deals with the opposition, which compromises their integrity in my eyes. Since politicians are necessary, we have to have them, but we don't have to like them. Too often, they get into office just so they can have power and make a buck. Since Trump is already rich, he can afford to be the least "politician-like" politician more than anyone else. He seems to hate politicians, just like I do. It also seems like he's mad about a lot of the same things I'm mad about, so he represents me and people like me as well as, or better than, anyone else I've ever had the opportunity to vote for to be President.
6. Since all politicians are corrupt, I'm not going to listen to people who try to tell me how crooked Trump is. They are being hypocrites by voting for someone who is also corrupt, so that cancels out their argument about Trump being corrupt, period.
7. Trump seems to be against all the things that I have heard about on the news (prior to the 2016 election) that I am against, so he represents me better than anyone else remotely running for President.