The older, ever-Tories were always going to vote Brexit, no matter what. Trumpism, however, played into the hands of a lot of younger people who themselves later admitted, as many of us know such people, that they really had no business voting the way they did - many went on to vote Tory for the first time ever & can't really point at anything that makes sense to them right now. They got played by Cummings & Cambridge Analytica. It's even on Cummings' blog, if he has not taken it down. So there is validity to both angles but the combination is what sealed it.