Well that's the question isn't it. Power corrupts. It is and always has been the way. At the moment democracy is the fairest system we have. But it doesn't contain any safeguards against electing extreme, populist candidates who may be damaging to their country and wider world.
I wonder if a parliamentary system functions as something of a safeguard against this. In a parliamentary system, a hypothetical Trump party might have been able to get a sizable number of seats, but probably not an outright majority (since many of the people who voted for him hated his guts, they just didn't think they had a better alternative), so he wouldn't be able to control the government without forming a coalition with another party that could act as a moderating influence.
