Because Rijkaard doesnt want to be some puppet coach which Galliani and Berlusconi ideally prefer and would want a proper project in hand not some team that feeds on scraps and free transfers with no vision for the future.
This is why many top coaches dont get linked to Milan
This is an essential problem for Milan. If mister whorebanger doesnt want to invest in the team, to a degree like Chelsea,PSG,Monaco,.. get funded by their owner, then he is a big handicap to milan.
He needs to decide wether he wants to make these investments or not. And if he doesnt, he should move on. Milan doesnt neccecarely need to be sold like Inter. But a new president that leaves the bloody coach to his work, could indeed attract far better coaches. And this selection of Milan is far better then their league position.