3) The Red Sox spent the money ownership allowed them to poorly
Part of the goal of the Chaim Bloom regime was to build a competitive team and restock the farm while remaining under the luxury tax. Bloom has done that pretty well, having a team that's remained under the luxury tax and in postseason contention for much of the year. They've been under the tax three times in his four years. The problem is, Boston making the playoffs once is simply not good enough for a fan base that expects to win consistently. Had Bloom done a better job with the resources he was given, maybe we wouldn't have this conversation.
The Trevor Story contract didn't make the most sense at the time if Boston wanted to keep Xander Bogaerts around long-term, and has aged extremely poorly. He's missed substantial time due to injuries, and when he has played, he hasn't been good. That $140 million could've gone to several other players.
Even a deal like the one Boston gave Corey Kluber this past offseason has aged horrifically. Kluber has been a non-factor for the Red Sox this season, and is making $10 million. The Red Sox have been needing starting pitching but instead relied on aging veterans with extreme durability concerns like Kluber, James Paxton, and Chris Sale. Look at what that's gotten them.
Bloom hasn't been given the same resources guys like Dave Dombrowski had when he ran the ship, but the money he has had he hasn't spent wisely. Had Bloom spent money better, Boston might not be in a battle for last and instead been pushing for a playoff spot.