Thomas De Gendt once made a comment about the amount of energy you save in the back of the peloton, compared to what is needed to stay in the front all the time. Can't remember how he described it, but basically, it was a difference of day and night. It's not simply a matter of staying at the front, and then winning the sprint. Staying at the front drains your energy, and very likely your sprint won't be quite as punchy anymore.Van der Poel positioning was questionable throughout the last 30 km, not just in the final.
He has tendency to slide back and then move up again from the sides, whereas both WVA and Alaphilippe almost never left the first 10 positions in those last 30 km. Of course having a stronger team would help, but he's also to blame. Not every race can be won by being brutally stronger than the competition.
