Players who don’t support United (or maybe even some that do) don’t think about the same things that we fans do.
They consider recent trophies and the set up of he club, in conjunction with the location.
Unfortunately Chelsea are based in London which is massively more attractive than Manchester to foreign players and they’ve won things, big things more recently than us, plus the manager has a bigger reputation that ours.
We love our club but footballers don’t really love any club, they just look at what is best for their careers. Really the only thing we do better than Chelsea currently is over pay players, which does attract a certain type at least.
Remove your emotion from it and look at it rationally instead.