Instead of crying over Pogba's departure, our board should think of how we will can convince him to stay. And we can only do it by showing him a plan and that we want to compete with the best.
Pogba seems like a loyal guy. He has lived shit while being in MU, when he was not appreciated and not given playing time. At the same time he felt appreciated here by being given a lot of time. He is very thankful of that. And has mentioned this in a couple of occasions.
However, as every good player, he seems ambitious as well. You can't expect by everyone to pull a Gerrard and stay at a club although he has better chances to win elsewhere. Splash some money, make some deep runs in CL and he might want to stay here.
Raiola is not an issue. He is a manager, he wants money, he invited bids. The first thing to care about is Pogba's intentions. Neddy had Raiola as a manager as well and he never wanted to leave.