Well, mostly because every time we say The Donald is great some ignorant leftward has apoplexy.
I honestly think that's a big part of it
I think a lot of his supporters just wanted to toss a spanner into the gears of the left. "hey - you want to go hard left and step on our rights, here's what we can do".
But the other thing is while trump's activities and what he said were often atrocious, his actual GOVERNANCE was pretty good. If you take the tweets and nonsense about how many showed up at his coronation out of it, the economy was good, trade went up, foreign policy was vastly better, he's the only president in ages who didn't start a war, Jobs were prosperous and his project lightspeed did in fact lead to the fastest development of a vaccine in the history of man. And for all his bluster he kind of stayed out of the lives of the average american.
Whereas trudeau - the results are very different. A country more divided than it's ever been, more than DOUBLING the debt from all the prime ministers before him combined, the trade deals have worsened and we arent' signing any significant new ones, the economy is in fact weak and is only holding on due to that massive gov't spending which has played a significant role in high inflation and will have to stop soon, he declared our modern day version of martial law on a bunch of protesters so he could seize the bank accounts of those who supported them, and then there's the actual corruption. The airports are beyond a disaster, good luck getting a passport, most of the gov't services are failing or have failed, and now interest rates are rising and we're going to have a significant recession. And before that the world banks predicted Canada's economy would now underperform badly for the next 40 years.
Honestly if trudeau had actually delivered and done his job right and we had a solid economy, reasonable debt and expenditure, and a modest blow from covid combined with a rock solid plan to get our finances back on track i think much of his other shenannigans would be forgiven. As was the case with Trump. But that specifically is where the two differ.