did he start sundance because he wanted to retire from acting

He started Sundance to help develop independent films. I think he planned to do more directing but the kind of projects he was interested in was not easy to finance.

It's that man again!!

I always felt that he had a bad excuse for starting a film festival compared to other people who start ones.

He started Sundance in 1980. He was no where near ready to retire. It was his ambition to "give back" and create opportunities for new artists and voices. The Institute is a lab where movie makers can actually create their projects with the help of mentors and Sundance is now the largest and most widely recognized independent film festival in the nation.