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.