I don't see what was so idiotic about Trentin's race. He put himself in a perfect position, did literally everything exactly right the whole race. It's not like he did too much work either, he just didn't have the power anymore when it mattered. In these conditions, strange things happen after 260 km. He got beat by a guy who was stronger at the end of the race, that's all. Van der Poel is a slightly different story, that looked like a serious error in judgement. Plenty of riders were suffering out there today but his collapse was remarkable.
As for the Belgian strategy, you can only say that was a complete failure. Not having a rider strong enough to join the decisive attack can be forgiven, but we should've had one of ours up front way before that point. What is the point of having a couple of big favourites in GvA and Gilbert and several dark horses like Lampaert, Naesen, Wellens and Evenepoel if they all wait, wait, wait and wait some more until, oh shit, it's too late? None of them did anything out of fear of losing their own, individual chance of becoming world champion. That's not a team. At least Evenepoel sacrificed his chances to help Gilbert, even if it didn't matter in the end.