But how do you reconcile Belichick "tearing it down to the studs and building from the ground up" with Belichick also re-signing 36-year-olds Brian Hoyer and Matthew Slater, 34-year-old Devin McCourty, and 30-year-old James White?
I don't think one excludes the other. All the plays you listed are on short-term fairly reasonable deals
Also, the last three are core culture, guys, for the team, exactly who you want around as you build in a new foundation.
Well, he's not tearing the team down with an eye towards non-competiveness and a high draft pick. He wants to compete next year so he is bringing back some vets. Plus, an experienced vet like McCourty is probably a good presence for younger guys in the secondary, and same for Slater (with ST unit) and White (for Mac). (Plus they gave very little money to White so if they need to cut him they can.)
The Mason deal I see as being about either thinking Mason has lost something and is no longer worth the contract or just about reallocating resources.
If anything surprises me it is that the team let Karras walk and then traded Mason.
But obviously Bill wants to do something else with that money.
I think this year is a bridge year. It may be similar to the Chargers last year. Last year, for the Chargers, Herbert was in the second year of his contract. They missed the post season. During this year's off season, going into the third year on Herbert's contract, the Chargers have already been very aggressive.
Chargers Off Season Moves So Far
I think the Patriots may be looking at their roster in a similar multi-year approach.
During this off-season, they have re-signed older veteran players (Hoyer, McCourty, White, Slater) on short-term deals as part of the bridge year approach. These veteran players can still contribute on the field (excluding Hoyer), but will, also, work as mentors for the younger players. They will help to teach the organization's philosophy to younger players. Long term, however, they are not going to cripple the team's salary cap in future years.
For the remaining off-season, I think the Patriots will spend the majority of their limited salary resources on cheaper players who can fill out the roster holes. Case in point:
https://www.sonsofsamhorn.net/index.php?threads/patriots-sign-texan-cb-terrance-mitchell-1-year-3-million.36086/
This approach allows them to go into the draft without any obvious needs because they will have duct-taped up all of their holes. This gives them flexibility in the draft so that they can basically allow the draft to come to them. Linebackers, corner backs, offensive linemen, receivers, etc. are still needs obviously, but if, let's say, a great safety drops to them, they can pounce instead of having to skip a great safety to grab an okay receiver.
Post draft, they can almost red-shirt their young players. Maybe in the later rounds they really focus on high upside players that still need to learn and acquire experience (someone like Joshua Williams, the corner back from Fayetteville State). Give those young guys a low pressure year to learn and adapt while getting indoctrinated into the team culture. That explains the veteran signings.
Then, during next year's off season, a lot of those veterans will be coming off the books, and a lot of last years free agents will be off the books (Agholor's contract expires after 2022) or at least easier to move on from. Edit: in addition, we can expect the salary cap to continue to increase with higher in-person attendance to games in a not-yet-post-COVID world.
Now, I am not saying that the Patriots off season next year will be like the Chargers off season this year, but conceptually it makes sense to build this years roster with a real focus on the 2023 roster as their opportunity, but I wouldn't be surprised if Patriots next year were able to trade for a good player similar to how the Chargers were able to trade with the Bears for Khalil Mack - taking advantage of teams that need to reset their rosters.
In addition to all of the above, the Patriots should be in line for some comp picks in next years draft (JC Jackson) which is another reason not to go crazy in this year's free agent period.
Edit: all that being said, I am really hoping that we get more than a fifth for Mason.