"Wasnt Billy Martin supposed to becoem a huge star ?"
He was highly touted. I think at the time he was the most successful college player ever ? I think Scott Davis may have eclipsed him some years later.
I saw him beat Harold Solomon in straights at the USO in '76. That was on clay (har tru). Solomon was a top player and among the best clay court players in the world. (I looked it up and "Solly" made it to the finals of The French that year losing to Pannata.).
What happened ? Well it's not that uncommon then or now that a strong junior career (or college) doesn't translate to the pro game.