They lost to another hockey country. S*** happens
Seriously. There's nothing wrong with Canadian hockey the world's just caught up with them. Or at least caught up enough that most games in the knockout phase have parity.
If you've paid attention it's happened at the NHL level too. The best d-man is Cale Makar, but Quinn Hughes and Adam Fox aren't too far behind, if we're being realistic neither is Hedman or even someone like Dahlin in a short tournament. The best goalies in the world are Shesty and Hellebuyck, Canada's best goalie is... Adin Hill? Canada does have the world's best centers (McD, MacK, personally I'd still lump Sid in here) but definitely does NOT have the best wingers. So, a strong but not dominant best-on-best roster at the NHL level. It's been like this for at least a few years.
Anyway imo this idea of Canadian exceptionalism in hockey is probably over, or at the very least shouldn't be taken for granted the way it's been for the past however many years. Yes, they should be expected to reach the semis most years but imo there are about 5 other countries (I'm counting Russia) who have enough talent to ice a world class team. Losing to a good team in the quarters isn't some crazy outlier result in my opinion, regardless of team construction and / or coaching