Burnley have already lost 1/3 of their successful keeper/central defence combination and the rumours are that the other two are going to agitate for moves. There's a significant chance that they'll do what we did in 2023 and sell their best players before the season starts.
EDIT: I see that Bellingham is trying to force a move away from Sunderland too. What's the point in promotion?
I was coming here to make a similar point.
I think 2-3 years ago, we were bemoaned for being so poor. My mate (not a Blade) said he didn't want us to go up last weekend, just because we were so turgid last time around. I argued that instead, we were just the first example of an emerging pattern/issue, and one that will only continue IMO.
The problem is exacerbated by the issue you describe. In earning promotion, the best players of the Championship now put themselves in the international shop window. They are less likely to stick around, due also I suspect to agents in their ear, reminding them that the year ahead is likely to be dire.
United: Berge and NDiaye
Burnley: Trafford, Esteve, Egan-Riley rumours
Sunderland: Jobe Bellingham rumours.
There is no sticking together, proving yourself at the top level, being plucky and maybe earning a move the year after, come what may. Instead, the move is starting to happen now, on promotion. The selling clubs, feeling the financial pressures no doubt cashing in on their prize assets now, whilst their stock is high - as opposed to a year later, after a year of drubbings and with their player going at a cut-price rate.