Belichick created the environment for Brady to succeed, it's that simple and irrefutable. Kraft hires any other HC in 2000, and we don't have 10% of the success we had. BB was absolutely brilliant in constructing that 2001-2004 team, as well as the 2007 team. Ushered in a whole new style of GM-ing in the cap era. Coaches and GM's throughout the league went to school on the Patriot Way, which was all BB. Then he led us to three more championships in '14-'18, and whiskers away from winning about 3 more. By far the greatest coach in history, even if things fell apart the past 2 years.
Brady was our greatest player, and any dynasty needs goat players, but this was Belichick's team. Brady walked onto a loaded TB team to win one last trophy (with Gronk by the way), then he also tailed off his last 2 years. The league is too good to win every year for 20 years no matter who you are.