Idiocy. The choice was never between Brady and Belichick. The choice was between the past and the future.
For the record I think we got the timing right on Brady's departure. EVERYONE KNEW that Brady had a few more years in him. We also knew that if we didn't retool for at least a year or two then it probably wasn't going to be enough to compete for Superbowls even with Brady. By timing it the way we did, we picked up Mac Jones, who isn't Brady but is talented and shows a lot of potential in his own right.
At the end of the day you've GOT to start thinking about life beyond Brady when he's 42 and the rest of your team needs to spend multiple seasons getting younger, then rounding back into shape. Brady's waited around through those periods before but at his age, chose not to this time. Gotta move forward not backwards.
Besides, Brady is partly responsible for the timing of his departure because, for completely understandable reasons, he decided that for the last few years of his career there would be no more hometown discount. It was basically a no fault divorce, everyone takes their assets, everyone would up happy with the outcome except a handful of superfans who still think it's 2005.