Well i don't really know the insights of that whole Donnarumma situation, but i guess that it probably went down quite similar as the situation with David Alaba and Bayern Munich. There, too, the contract negotiations dragged on forever and in the end there was no agreement, which probably neither party had expected at the beginning. That was bad for Bayern, of course, because they have now lost a player with a market value of €60 million without getting even 1 cent for him.
Probably the same happened with Milan and Donnarumma and in addition to that i guess no one at Milan expected that Donnarumma would be named the best player of the EURO 2020. If Milan would have known that before they definitely offered him a better contract.
Even before euro 2020, this was a kid at 22 became worldy known goalkeeper. I would not name him the best goalkeeper ever but I have to say it is definitely one of the best goalkeepers even if not THE best, and he is only 22, so you can get at least 10 years out of him, maybe some more. This was all known, Alaba situation baffled me as well. I just simply do not understand it when teams have players that worth a lot of money and then they just do not do the contract negotiation the way they should be doing it.
I get that you may not like to give the player some extra 3-5 million or even 10 million, but even in that case just give him whatever he wants and then sell him, that is a lot easier to just lose him completely that is just surreal. Yeah they didn't give him what he wanted, and now what? They lost 60 million euro from not being able to sell him, is that better than not giving him some more money? Even 10 million more per year would have been 6 years to get there.