It is hard to believe Chisholm when he says that the recent purge of Holiday, Porzingis, Horford, Brown, and so, was not financial. Of course it was. But that does not mean it was entirely decoupled from basketball reasons. For example, you can pay Brown, give him an extension meaning you are paying him for several more seasons, or you can trade him and use his salary on different players.
As it stands, they took back George so there really is no additional "optionality" right now, but if they had kept and extended Brown, there would have been no optionality for about 5 more seasons. Now they have a path to optionality (not saying I like the deal, just offering what I believe the thinking was). They are going to spend the same in any case though, even after George is gone. They will stay between the tax line and first apron. I expect nearly all teams will. It is just what do you spend it on.
BOS was willing to pay two max deals to Tatum and Giannis, but not Tatum and Brown. Is that a financial decision or a basketball decision? I think the difference between Brown and George is that Brown would have expected a max extension, and BOS did not want to go there for both financial and basketball reasons. If you have (2) max deals, you can't do much else. You better be sure the (2) max guys are really good.