Stallman's smart enough, probably on par with Gates and Jobs. The problem is that he's more narrowly focused in his intelligence. That and he believes that proprietary software is inherently evil.
To be fair a lot of companies that sell proprietary software have exploitive business practices and Apple's one of the worst. That kind of thing is what helped form his opinion of proprietary software. Stallman goes too far the other direction in my opinion with his view that all software should be free. As far as I'm concerned there is a place for both FOSS and proprietary software.