that he's so much stronger than Ngannou? Mark Hunt? Rothwell? i don't think so. i think he's strong, but i don't think he's so much stronger than those guys that his strength enables him to do stuff they can't. Mariusz Pudianowski is a 5 times world's strongest man winner and i've never seen him be able to get up from under people the way Derrick Lewis can.
i think people are underestimating his skill and fight IQ. there's a couple of things i see that allow him to do these things the other HWs can't. he understands how leverage works. he knows how to create scrambles with minimal effort. he stays calm without wasting energy and can feel when to explode.
if he was only using strength to get up every time he'd gas after getting up only 1 or 2 times, but he doesn't, he can usually keep getting up from under people as long as they don't go for rear nakeds.