Per a new interview on the Rich Eisen Show, Mike Holmgren said that he reached out to the Niners when they had their coaching vacancy following the departure of Jim Harbaugh. He believed, at the time, that he wanted to get back into coaching, if the right situation revealed itself, and the job with the Niners was something that fit what he wanted.
However, San Francisco got back to him and said they were going in another direction. That, per Holmgren, was the sign that he should remain retired. Listen in.