Stills was a lesser known than a lot of the others on that card in 72. CSNY had Joni Mitchell and the Beachboys with them in 74. You didn't answer how many people were there but I'm sure you looked it up so I'll just say it. 75,000 ... beat any harness venue ever.
In 72 it was a multi day affair and attendance was estimated at between 15 and 20,000 which was way under expectations. The other stars that year were Chuck Berry, James Brown, Ike and Tina Turner, Sly and the Family Stone, Shirelles, Bo Diddly, Stills, Commander Cody, Sha Na Na and Jefferson Airplane (what were they doing in that mix)?
Must have been too many black groups to ramp up attendance back then on Long Island.