Prior to 1950, the mound was NO MORE than 15" and teams adjusted it between 0-15".
Between 1951 and 1968, it was set at exactly 15", giving the advantage to pitchers.
In 1969, it was lowered to 10".
For me, mound height had a lot to do with pitchers being able to throw without much stress and exertion. When they lowered the mound, it became more stressful. Additionally, certainly pitches create stress. For instance, the split finger was in vogue in the 1980s-1990s and many a pitcher that threw that pitch or a fork ball had arm issues.
Greg Maddux did fairly well be just mixing speeds and spotting his location. Today it is all about the velocity and the art of pitching is gone. Frank Tanana went from a flam thrower to an effective pitcher once he had arm trouble.