He would have won exactly zero titles in NE without BIll...the guy was a 6th round pick that was developed by Bill and his coaching staff. Other teams would have cut him and Brady would be selling insurance with his dad. The chances of a 6th round pick becoming the most accomplished QB in NFL history are about as great as your chances of winning the lottery.
Unitas, maybe the best QB of the 50s, 9th round draft pick, 1 Super Bowl
Starr, maybe the best QB of the 60s, 17th round draft pick, 2 Super Bowls
Staubach, maybe the best QB of the 70s, 10th round draft pick, 2 Super Bowls
Montana, maybe the best QB of the 80s, 3th round draft pick, 4 Super Bowls
Kurt Warner was undrafted, won 1 Super Bowl, one of the few to bring 2 different teams to the Super Bowl
Winning is not always tied to the selection in the draft.
No. Brady was not good in college and was not good in 2000. Bill developed him into a very good QB and then he became an elite QB in 2007.
Belichick, Weis, Tom House, Scarnecchia, and others contributed greatly.
Brady was good in college, the narrative going into the draft was why Lloyd Carr was trying to replace Brady with Henson all the time, and scouts took that as a red flag.
But that's not the point. Coaches are teachers, they do not 'develop' players. Some teachers are better than others, for sure, but the development is what the player will do himself to get better at his craft. For example, if Belichick was so great at developing QBs, then why wasn't he able to develop any other QB other than Brady that went on to have a long and productive NFL career as a starter ? Davey, Kingsbury, O'Connell, Robinson, Mallett & Etling were never starters. Brissett is a career backup and Stidham is heading this way too. Garoppolo was a starter for 4 years, and now he's a backup at 30 years old. Cassel left the Patriots at the age of 26, and started more than 10 games in a season only twice in his career after the trade to the Chiefs.
Belichick lost the recipe to develop QBs after Brady ? That's not a knock on Belichick, he put Brady in the best position he could for Brady to succeed, but it took specifically Brady to get the Pats to the Super Bowl, nobody else came close of being 'developped' into a long time starter.