Well he's a France international and starts a lot for Juventus, that looks attractive to a team like Everton. Also with Carlo being coach it makes moves with them a bit more likely.
I think you'll see a few more of these swap or swap plus cash kind of deals this summer. Still, the rumour seems like a bit of a re-hash. Why would Kean even come back? Unless he is going to be promised Morata's spot.