Management just don't believe in Immobile. That's pretty much it. They want to sell while he's up. Only time will tell if Marotta and co were right.
Instead, we're investing in a cheap player (Morata on loan + option to buy) to be Llorente's backup. And Gabbiadini can very well play as a CF. This is the management's point of view.
I don't like the Morata deal, we shouldn't bow to Madrid like this. If he pans out, we'll lose him in 2 years.
On the other hand I'd really like to see what Immobile can offer us. Imagine if he does poorly... 6 goals in the season, Conte doesn't trust him, struggles to get playing time. Even in this situation, he'd still have a great market in Italy - his value wouldn't drop to less than 10/12M. He could still be sold. IMO he definitely should be brought back.