I'm really not sure what point you're trying to make. If you went to the first one in 1970 as you seem to claim you'll know there was theatre and films plus a light performance actually advertised on the poster plus plenty of other stuff. The second festival went further with "dance, poetry...
What "other crap" are you talking about? Whilst music has always been the central plank, it has always had a broader remit. It's what has made it so famous and the greatest festival there is.