I remember Trump favouring Carney more than PP during the campaign for the federal Canada election. I don’t fully understand it

It was dead simple. every Conservative politician both here (and the few who cared there) was essentially screaming/signalling as hard as they could to donald to STFU about Polievre as their relationship was huge wedge issue in the Canadian Conservative party. (Donald also rarely likes backing the losing side.)

Not to be rude, but it seems like you're fairly new to politics if this was something that was honestly confusing. So, if I can offer some friendly advice/perspective: Carnery is handful of months into a new term with Canada facing arguably the largest economic crisis of the last 30 or 40 years? An almost unprecedented upheaval to our economic system in that our single largest trading partner (we trade more with America than we do with the rest of the world combined) now wants to decouple. The Liberals barely won that election, and even with an almost historic consolidation on the Left, could not assemble a majority. At the same time, Left wing governments across the world are embattled as far Right movements rise in popularity (Germany, the UK etc.)

How we approach the next few months likely has generational impacts that far outweigh an EV mandate next year or the next five. That's a time to be cautious, measured and compromising, especially with those with whom we disagree. I would prefer more stringent climate regulations but what matters most is that we can carry those out long term. How do we do that? On some aspects of climate, we're probably going to have to compromise (EV mandate) and on others (say, doubling oil production) we're probably not.

I fear Canadian politics is descending to the 2-party system

Because almost half the country went Conservative. They got more than 40% of the vote. Even adding together every Green, NDP and Liberal vote barely gets to 50%. Either the centre and the Left fracture and let the Conservatives do whatever they want, or we appeal to some of that 45% and get back to our regular multi party system. But as long as the centre and Left so repel 45% of the population, that's just a recipe for actual climate suicide, not this "oh no, Carney is the same as Polievre" silliness." Especially in our elected dictatorship, it's a great strength of our system but also means that there is a huge risk.