Mac was huge even when he first came up in 1986. He hit 49 homers in 1987. He was always a big slow power hitter. He admitted to using creatine which is perfectly legal. But it's not like there was ever a major change in his body type and he had massive power even as a rookie.
Bonds was pretty skinny and fast when he came up, with moderate power. Then suddenly after he moves to SF he gets real burly and slow and his hitting 40 to 70 dongs a year. Some of it is aging but for a guy to change his body type like that, and then his trainer is busted in a drug ring, it doesn't take a rocket scientist to figure it out.