Really smart people have better things to do than spend all their time on chess.This proves that really great chess players are stupid. Bobby Fischer was the perfect example. And Zod is an imperfect example.
Therefore, yes, stupid people may and can play chess...often to excellence and beyond.
(I don't actually know what is "beyond" excellence but it has a nice ring to it.)
Or can any individual become successful in chess?
Likely, if they start early enough (age 3 or 4 say) and spend enough time on it. If you're an adult however and the brainpower is not there, it will be tough going.
Another way of saying this is that talent and even intelligence in an area can be developed. However, after a certain age, it becomes much harder to do so.