I don’t think the club “fear” him leaving at all. In fact I think they believe it’s inevitable relatively soon and already have superb options lined up.
As said above though he didn’t sing the contract offer so hardly surprising TB didn’t give him big signings. Suspect TB keeping his gunpowder dry for a serious strengthen in the summer, potentially with an RDZ upgrade.
I’m not having Fati is a RDZ singing. He helped convince him to come but there is zero evidence that he was his player. Also, are we actually talking about the Fati whose performances are a big reason we have performed well in Europe? Before his last injury he was looking class.
I’m certainly still pro RDZ but a manager has to get a good tune out of the players he has. And RDZ still has very good players to get a tune out of. A good first step would be to get the team to be capable of defending and not giving away horrendous goals every single game.