"Maniac" and "fringe" have no absolute relationship. Look at Hitler. I'm not exaggerating. Let me quote Wikipedia: "On election day, 6 March 1933, the NSDAP's share of the vote increased to 43.9 per cent, and the party acquired the largest number of seats in parliament."

I'm not equating Trump and Hitler, btw. But Hitler proves that being mainstream means nothing.

Separately, it is also my perception that both men's source of power are somewhat similar. They both have supporters that want an aggressive, authoritarian leader to change things drastically because the current direction isn't working for them. I think that's a dangerous thing to wish for.