I believe he cracked in the Vuelta because they got his nutrition wrong, trying to loose weight too fast or during the Vuelta. All signs point to that imho. They sent him to the Giro with a weight they considered ideal for that race, so they didn't need to start messing around with his diet. So he would not have experienced in the Giro, the bonk he experienced in the Vuelta.So given how he cracked from being too heavy in the Vuelta, he wouldn't have been able to contend for the title in the Giro as he was also too heavy there (in hindsight)?
However, that does not mean i think he would have sailed through the mountainstages. Imho, it would have been a struggle for him due to his weight. But i do believe he might still have won the Giro, for two reasons. First of all, without covid the outcome of his two last stages would have been more favorable. He probably wouldn't have lost time the stage before the TT and he would have gained extra time in the TT. And two, Van Wilder lost roughly about 5 minutes since he started riding for GC and after his time gained with the long break. He is the same size and weight as Evenepoel, similar bodytype. So while i think he would have bled seconds in the last week here and there, it might have been enough with a nice buffer. I also think he would have gained time in the last TT.
But overall, i think the two GT's where they got his weight in the ballpark, were Giro '21 and Vuelta '22. They supposedly poached one of the Visma nutritionist for this year. So i'm crossing all my fingers and toes.