I think what happened is that it became more acceptable to show their nastiness; that they used to have to hide it because our society wouldn't accept it. Then Trump being elevated to president normalized the violence and hatred being out in the open and those people felt safe to come out of the woodwork.

I feel like it was always there, simmering beneath the surface, but I'm a self-admitted (overall) misanthrope who thinks most people are, on average, pretty shitty.