If he stays until he retires at Tottenham there is a possibility that Kane will become the top scorer in the Premier League, but for what? What is clear throughout his career at Tottenham he has never felt the EPL tofri. Yes i agree with you that Kane is better off leaving in the transfer window this season than staying. Considering that there are three advantages here that i see, firstly Bayern Munchen can give Kane the championship trophy at least in the Bundesliga. Both Tottenham will receive a sizable amount of money from the sale of Kane and can bring in new players, if not released next year Kane's contract expires and he leaves on a free transfer. The three Kanes have become top scorers for his club that's enough, now moving to Munich and winning a trophy will complete his career.

I assume that after comparing the two clubs, we can all agree that Munchen is better than Tottenham for now. Thus, joining Bayern will take him one step further to win a trophy.