Well a couple of things, he couldn't adjust to Everton's style. Juve obviously have a lot of the ball, and can play more in the final third and Everton just didn't create many chances last season.
I actually think if he came on this season as a sub, he would have done ok, but seems as though Carlo thinks Kean is behind Iwobi and possibly Milik/Llorente if they come.
Last season was a horrible time for him to come.
Few games where he started and he was screaming when he missed an opportunity or made a mistake. I think he put a lot of pressure on himself too.