The guy made the right decision - Sha Na Na was the phoniest things in rock there ever was, before the Blues Brothers and Spinal Tap, that is. But how that stint inspired him to take up linguistics is not entirely clear.
By the time Jimi played, there was only 10% of the Woodstock audience still at the show (no joke). 40,000 people remained out of 400,000.
I guess Sha Na Na did the job they were hire to do. "Get them up, get them out..."