After reading the Wikipedia article and so forth, yes the man was smart. For instance it says he was writing business software as a teenager. It also says that

After reading the Wikipedia article and so forth, yes the man was smart. For instance it says he was writing business software as a teenager. It also says that Altair BASIC was initially written on an emulator, which was itself written by him! We're already at the clever and talented point right there. "He scored 1590 out of 1600 on the SAT[19] and enrolled at Harvard College..." isn't a perfect indicator but suggestive also. He might have had other breaks in life but smarts would have been one of them.