Who would vote for such a clown, they thought. Then people joined the loltrain of populism. Pundits chose to ridicule, and that fed the positive feedback loop.
So much for dubious causality chains, but it's not uncommon today to assess that not caring back then, and not being prepared to combat the absurd, catapulted his fame.
Failing to properly combat imbeciles, not caring, leaves the system open to said imbeciles having a chance to gain power.
That people care about, and aggressively combat, any kind of stupidity leaves that kind of imbeciles at bay.
We may read that the US is safe from a Trudeau-type populist clown because people combat PC. People combating the other end are, apparently, less experienced, or are actually the imbeciles themselves (and, mind you, the fascist trashing is an imbecile-tier tactic), so you get Trump.
Or we may read that having Trump is an asset to have a fairly unpopular Hilary actually appear as the reasonable alternative.
Either way, the end result is shaped by those who cared.
It's alright to be uncaring and unconcerned. Most people are. Heck, I even applaud people that don't vote: it's their right to be unconcerned.
However, when someone proposes that callous apathy as an ideal to follow, they'll be rightfully laughed at: because they're choosing to be entirely worthless.