how so? have you actually seen any of his fights?
he won the bjj world championships at blackbelt 4 years into training. that alone was unprecedented, he was a true jiu jitsu prodigy. came into mma, and instead of outgrappling everyone like most people would expect from a bjj prodigy, he went ahead and knocked people out instead. din thomas and caol uno were both top 5 in the world at the time, and he knocked them both out in the first round, in his second and third professional fight. this, too, was unprecedented.
so we're talking about a guy with jiu jitsu skills matched by very few people on the planet, who routinely knocked top competitors out, who had impeccable takedown defense, and rather impressive takedown offense as well. a guy who by today's standards would've been a featherweight ended hughes' reign, fought as high as fucking heavyweight, took the lw belt and gave some top welterweights tough fights even in the twilight of his career.
penn's issue right now is the fact that he can't hang them up. he's a decade removed from his prime and keeps fighting, so he keeps getting trashed. and jerkoffs who have been following the sport for 2 months are now giving him shit because he keeps losing... as if it fucking matters.
so to me, it seems more like you don't know jack shit.