I will not discuss the problems experienced by Dele, but rather the character of the player's game.
Dele Alli's playing style is similar to Frank Lampard's. Dele Alli is more modern than Lampard. Of course Frank Lampard has been monitoring DA since he coached Chelsea even before he coached Chelsea. Therefore, I believe that Dele Alli will find his rhythm again under Lampard's tutelage.
It will be very synchronous for a club if a player is coached by experienced people like Lampard because at the time when Lampard was still active as a player in a club, he was also a star even though his fame may still be very little compared to other stars, but seeing this could happen to Lampard and DA, then that club would also be very profitable.
It doesn't always go according to plan. Everything needs a process to reach the best level, whether for the club or the player. There are also former great players who are now coaches but failed to bring the club to the championship track even though the coach recruited great players.
In terms of Lampard and Dele Alli, we'll see if they reach the best level?