It's 2:30pm EST and I am just learning about all of this. Holy moly.
I am really curious to read the articles that come out explaining what really happened behind the scenes. My guess is:
1) Ainge has been thinking of stepping down for a while now, especially given his heart troubles.
2) Stevens was exhausted and wanted out, and the team was open to the idea. His transition to Ainge's old seat is being billed as a promotion, but it's really that Brad has time left on his deal and the Celtics want him to stay on to help with the transition and project the image of stability. There is no way that Stevens is permanently retiring from coaching at the age of 44.