It's hardly appropriate from a United fan right now to discuss to much about Spurs downfall, however, i do think there is a critical difference here. United has a very young team and is well in the process of building up experience to the youth (not just academy players but Bissaka, James, Rashford, McTominay, Martial are yet to reach their peak) and also have the financial power to fix the problem areas of the team. Now, if this will work or not is another matter. The problem is Spurs will most likely need 2 new CDs, probably 2 new fullbacks, a new creative mid...that is a lot for a club that doesn't like to spend. Things will get worse for them before it gets better, while United and Chelsea have a chance of building something that has already started this year.
Kane, like Berbatov, Carrick and Walker before him, is probably thinking of leaving for the sake of his career, as he should imo.