Even Belichick has said the 2001 win was totally unexpected.
I take that with a grain of salt.
Not expected, due to it's only his second season as head coach. All the planning, drafting, organizing was built for the long term - Bill, as usual the smart guy he is, applied a lot of the lessons he learned in Cleveland. Among other things, shrewd salary cap management.
Brady changed the dynamic. Like the Bruins in '11, the '01 Pats won the title without sexy super stars. As the season progressed, they displayed the ability to make clutch plays, as well as the discipline to execute fundamental, seemingly ordinary plays in high pressure game situations to consistently win. Mike Martz, for one, flatly stated to his team after they took a physical beating in a hard fought victory in Foxborough, "That's a Super Bowl team."
My qualifications extend to being a couch potato and sports page addict, but after decades of watching the sport there were clear indications the team had very high potential, in my opinion similar to a previous Patriots edition thirteen years earlier:
A young, talented team with a sprinkling of veterans; lots of players with playoff experience and several with Super Bowl experience; a first-rate tough defense*; a poor start to the season before a young, gifted quarterback got his first extended starting opportunity, foreshadowing a record setting Hall of Fame career**; a solid running game*** and talented receivers; positioned down the stretch to qualify for and compete seriously in the postseason.
*1988 Patriots defense: 5th in NFL in points allowed
2001 Patriots defense: 6th in NFL in points allowed
**Flutie: CFL
Brady: NFL
***John Stephens, 1168 yards
Antowain Smith, 1157 yards
The 1988 team had impressive victories over the Bears (NFCCG) and Bengals (SB instead of us).
The difference, of course, is the decision made by the head coach. Bill made the right one, but it was the difficult, unpopular, unsafe, unconventional one - which I and lots of other Pats fans completely agreed with.
Even the great Red Auerbach later admitted he was mistaken in dismissing Bob Cousy as nothing more than a "local yokel". Raymond Berry had no such epiphany, abruptly benching the winning Flutie, and the team was promptly eliminated.