Do you realize that Tottenham's decline occurred when Harry Kane left the club?
Tottenham has always been the same to me, same team that their performance can never be relied on. Last season looked like they have already progressed past the stage they are in already, but they are back there. Richarlison was expected to be a replacement after Harry Kane, but he could not fit that shoe, Solanke who has joined the club is not receiving enough support from other players in the club to score goals, they do not pass the ball to him often maybe also because they do not yet trust him enough to deliver.
I don't expect them to sack the coach just yet though. He should be given more time to try fix the team.