Don't you think that if something else was the prevailing factor there would have been more than 3 people cranking out those numbers?
The only good argument to that is that those 3 would have been the elite power bats of that generation with or without steroids, but, I think Sammy Sosa debunks that theory.
No I don't think so. If steroids were the driving force we would have seen these numbers every year for 10 or 15 years straight since such a large portion of the player base was using back then. The fact those were focused into such a small period pretty much makes it impossible for steroids to be the driving force. Steroids might have made Sosa a 40+ HR a year guy, but something else made it jump to 60+.
McGwire walked into the league as a 40-45 HR type player. He likely got on the juice during his injury years and walked out of those as a 52/58 HR guy. Then expansion hit and the juiced balls and suddenly he was 65/70 HR guy. His talent gave me him a big chunk, steroids gave him another chunk and then other factors pushed it to the record levels.