Trudeau keeps getting in for a couple reasons:

1. The average Canadian has less than ZERO understanding of politics. Both law and political science are elective courses in high school. there are no civics classes. They vote based on, well stupid reasons. He got in initially because old people remembered his father and young people were lured in by the promise (which he kept) of legal weed. And he's not terrible to look at.

2. We have 3 main parties, one right of centre, one left of centre and then the Liberal's, Trudeau's party that rides the middle and swings one way or the other depending on how the wind is blowing. Then we have some lesser parties, the People's Alliance, on the right, the Greens and the Bloc Quebquois (which is a Federal party but only for the province of Quebec). This all adds up to both the right an dleft vote being slpit and Trudeau coming up with more votes than any other party, but not the most overall, if that makes sense.

3. Lack of viable alternatives. Keeping #2 in mind, there's also the problem of less than inspiring candidates and party leaders.

I can't run for office. I tell the truth, LOL. Seriously, I can't, I'm a polarizing figure, people either love me or hate me, there's not enough middle ground for me to be viable.