Not for lack of desire, probably; emigration is really difficult.
If people were that bothered about Trump they would do it. It's all bullshit it just sound good doesn't it "If Trump wins I'm leaving America yada yada yada"
Emigration takes a lot of time and money. Finding a destination country where you could reasonably make a living, which would be willing to accept you, is definitely not a given. It seems completely plausible to me that many people might say "if Trump wins, I'm leaving" with complete sincerity, only to later learn that they cannot actually accomplish this.