But compared to the rapid rise of other financial factors like college tuition, stock market isn’t over valued...
Those are 2 different things and not comparable. College tuition and healthcare costs have gone up much faster than inflation because it is purely a demand and supply situation. Lots of demand because of how ridiculously easy it is to get educational loans. Students can borrow not only for tuition but also for housing and auto and travel! And who can avoid going to a doctor when really sick!
On the other hand, most corporations do have competition, both domestic and foreign, and their stock price therefore is never a monopoly and therefore has to be performance based.