It's all just for fun, since we will never know and everyone has it right in their own mind. Would Evenepoel have won the 2020 Giro if he hadn't crashed? Judging by who actually made the podium, i would say yes. He had a good winter, he was in good form all year, had no issues with his weight or illness, he was comfortably beating Ganna in TT's and was one of the best climbers in races before his crash. Very high probability he'd have won.
Giro 2023 had he not been struck by covid? He was "competitively overweight" imho. Everyone except Flanders could see it, and they admitted he was more than 2kg heavier compared to the Vuelta he won. So i am slightly more hesitant to claim he would have won that Giro, but i would say more likely so than not. Ultimately, i'm going to say confidently yes. Why? Look at how close guys like De Plus, Arensman, Van Wilder, Dunbar, Leknessund, Kämna... stayed in GC, imho the level in that Giro was also not too high, that i'd given him well over 50% of winning that Giro. Those guys lost time to Roglic over 3 weeks, that they would lose in half a stage in the TDF.