Not unusual for NE to take a calculated risk. What is unusual is that in addition to the health issues, there were concerns about Easley's dedication to football and his character. Maybe having Wilfork, Mayo, McCourty etc. in the locker room is part of the calculation, but BB went against his own philosophy in this instance. Best case was that the player was an unusual talent that could have been a potent defensive weapon. Did BB feel the upside merited the gamble? Apparently he did.
Call it what you will - bust, mistake, whatever. This time it didn't work out. My guess is that BB is highly introspective and thinks a lot about decisions that didn't pan out with the intent of making better decisions going forward. At the same time, he doesn't beat himself up to the point of being afraid to take a risk. It's also worth noting (once again) that Bill doesn't fall in love with his mistakes, so when it's time to cut his losses and move on, that's what he does.
What's pretty clear in this case is that the player repeatedly pissed off the big guy a lot, to the point where Easley not only got fired, but is getting his all of dirty laundry rather explicitly aired on TV, radio and the internet on his way out of town.
I wish the whole thing had never happened, but good riddance.