Even though Tottenham Hotspur are known for sacking their coaches who take them to a final or win a trophy for them, I think Ange Postecoglou's case is totally different. Tottenham Hotspur finished in 17th position in the Premier League table, and Levy is afraid that Ange Postecoglou will likely not perform better or help Tottenham Hotspur compete in the Premier League next season. So, for Levy to avoid any poor performance from Tottenham Hotspur next season, he decides to relieve Ange Postecoglou of his duties at Tottenham Hotspur so that he can get another coach who can help Tottenham Hotspur compete in the Premier League and UEFA Champions League.
Next season Tottenham are going to play in the Champions League, a competition which is clearly above their level so, in my opinion, the best case scenario for them is to reach the first round of the knock-out stage, that's it. I can't imagine Tottenham at the quarter finals or semifinals. At the same time I expect Tottenham to perform way better in the Premier League, this season they clearly focused on the Europa League, and they won the best.