Donnarumma reportedly demanded a pay rise, but PSG management was reluctant to agree. Other reasons, Luis Enrique is reportedly dissatisfied with Donnarumma playing style, although he admitted that letting him go was a difficult decision. There may be a lot going on that we don't know, but it's clear that several clubs are very interested in signing Donnarumma. We'll have to see where Donnarumma goes, and it must be admitted that the way PSG treats him is disappointing.
If he demands a pay rise from the team, it certainly won't be immediately agreed to, as PSG also has significant salary obligations for other players. Furthermore, PSG's players have improved significantly after winning the UCL last season, so PSG must find a suitable replacement if Donnarumma is their final option. But why do you say letting Donnarumma go is a difficult decision for PSG, given that he is being targeted by other teams?