Looking at Bill Madlock's 4 batting titles, it appears it's a case of quantity over quality. Durability seemed to be an issue his entire career as he topped out at 154 games played in two different seasons.
Here are the games played each season he won a batting title:
1975 = 130 games
1976 = 142 games (hey at least he won back-to-back titles!)
1981 = 82 games (strike shortened season obviously)
1983 = 130 games
So is it just a fluke that he won 4 batting titles? Victim of circumstance? Does this say less about the quality of NL hitters in the 70's and 80's? I'm still blown away that he has 4 batting crowns!