The philosophy of science suggests that most theories are false. When a theory approximates the truth then that is progress. Mike was probably wrong about hypertrophy but he was consistent in what he wrote and that is still an impressive treatise.
I think just about everyone underestimated Arnold's intelligence. If you judge a person by what he has achieved then Arnold's record is outstanding when you consider he succeeded in a foreign country. I mean, how lucky was he to portray a machine in those science fiction movies? His accent helped him because he seemed foreign. The Terminator from the future should have had flawless English but there you are, a glitch, but believable on the screen.
I never felt Arnold was that smart and perhaps neither did Mike. Arnold exceeded us both by a wide margin when it comes to motivation and determination. Most people give up but not guys like Arnold. They use people and find a way to succeed when completely against the odds. That take an exceptional person to do that.