Because the people in Milan thought PIF were going to buy them and can't accept that Serie A's **** financial deals didn't make it worth their while. They've slagged NUFC at every stage ever since even doubling down saying PIF still wanted to buy them etc.
Nobody likes the new guy who plonks himself down at the top table without invitation and immediately picks out the juiciest best looking steak. We are that guy so we best get used to being hated by folk you never even thought could care about us. It'll be alright, our money will still be good when its way over the odds