Fans sense John Henry isn't all-in on his Red Sox like he once was, because his most recent Chief often didn't spend what it took to land or keep many players viewed as potentially vital to the success of the team. But success doesn't necessarily always entail just winning...
... not if you accept that watching, following and rooting for a sports team is a form of entertainment, an interactive hobby, a not-just-passive pastime.
Red Sox fans want star players, but love good guys who try hard and at least look and sound like they care as much as their fans. Since baseball is a young man's game, homegrown prospects are the easiest to grow attached to as they develop into big league regulars (and hopefully All-Stars). There are also veteran warriors who show they have what it takes to thrive in Boston and on a big stage.
Those are the guys an owner should always pay to keep or recruit. A core to care about. When fan favorites like Betts, Bogaerts, Schwarber and Eovaldi leave, in lieu of cheaper, revolving replacments, there is a detachment.
It's not just about rooting for the laundry.