No, he needed a defense in order to win. The Niners had good offensive skills but they had good defensive players as well. Ronnie Lott was a monster.
As I said before the Niners were a team built (and built well) for the passing game. A team like this recruits good QB’s (Young was the best second string QB in the league for years, then came out of Montana’s shadow to become one of the best QB’s in the league) and then drives up their numbers.
And winning Championships doesn’t hurt either.