The thing with Van der Poel is that he is generally going faster than most (everyone). both on road and on dirt Inevitably there will be crashes.
Addressing the WC Road it was super slippery and he was not alone to loose grip, yet he was going faster than the chasers (WVA, Pog, Pedersen).
WC MTB was a bit "bad", maybe he slightly overcooked himself by going max from start and joining the front in a very short time. The front wheel slip looks sloppy but anyone who rides will know that it can happen. The OC crash was worse and incomprehensible. Cannot really get why they didn't recce the course better? Overconfidence? Yet he won the MTB EC XCO in 2019 so in principle he can win any MTB race he choose to race.
CX is just a bad place to draw any conclusions from his crashes. He goes faster than everyone and there's always that risk of going down. "Safing" is just not a way to win. He is the most successful CX rider ever so that speak words. Some CX riders loose some (much) of their technique when in red but MVDP has consistently proved to be able to keep it together.