PFT offered an interesting hot take on why it took until now to sign. He was waiting for the schedule to come out. Without Rodgers, the Steelers wouldn't be as interesting to the networks and they would get fewer prime time games. Last season SHOULD have shown us that it is an overall advantage to play your games in the one o'clock window. Also Rodgers experienced how a season full of "prime time" games can be detrimental when he went to the Jets.
Now I don't know if this has any truth to it, but it DOES make sense. I don't know if this signing means he will report for any of the voluntary portion of the off season, though I suspect he will. I still hate Rodgers going back to the early 2010's when there was the controversy between who is better, Rodgers or Brady and we all were busy finding stats that showed that while he was obviously more gifted athletically, he wasn't CLOSE to Brady in his impact to the winning of games. IIRC, my favorite one was Rodger's lack of 4th quarter come from behind wins. I don't remember the numbers, but Brady had a LANDSLIDE (yes. it was more than just lopsided) majority).