The feck? Have you ever worked in a big company where there is uncertainty? A toxic atmosphere? All that shit spills down to EVERYONE. The squad isn't on an island away from the company that is Manchester United. It's not just executives. Staff members of any level don't know if they'll be in a job for various reasons. Having a drawn out sale process will inevitably have a huge impact on every aspect of the organization.
The players always live with the uncertainty of their careers being tied to athletic performance. But it's the mood. The mood at every corner. The mental image everything sets to the players. The motivation and drive and admiration and togetherness. That atmosphere spreads to the team, and it has an impact. When you have that much negative publicity as we've had this year, add in injuries which in turn leads to questionable decisions by the manager and him now making some mistakes, things can quickly slip. If the rest is a mess, it makes the actual club morale a very fragile thing. If it's strong behind the scenes, set, secure, leading the way and striving to be the best... Then you are much better positioned to deal with any set back. As it is, United the club just give a hopeless feel to all fans, staff, and players.