They would not want Harry Kane if only Sadio Mane could show the best game he has, but Mane was unable to show his best game last season so Bayern Munich began to shake and look for players they thought would provide the best in their squad. Harry Kane's name also emerged and was considered to fit what Byern Munich needed. I think the change of coach is one of the factors why they are looking at other players, because it is likely that Thomas Tuchel does not really see Mane in the game scheme he will play. But it will be very difficult to convince Tottenham to release the player.
Actually Mane is not a center forward like a replacement for Lewandowski, his main position is to play on the wing. however, due to his age, it is hoped that he can adapt to playing as a center forward. unfortunately, Mane needs time to adapt to his new position. plus, the system used by Nagelsmann is very different from Klopp like when he played for Liverpool. actually, I'm pretty sure if he's given one more season he can settle in pretty well. Unfortunately, Tuchel doesn't want him to be part of his project. because, Tuchel prefers other players. plus, the incidents of Mane and Sane which made his future even more uncertain with Bayern Munich.
Now Tuchel prefers to overhaul his squad, he is more eyeing Harry Kane as Lewandowski's successor. even though, Mane can actually be maintained to play on the wing. However, Tuchel doesn't see him as an alternative. especially to bring in Kane from Spurs, Bayern had to spend quite a bit. to reduce their expenses, as a result Sadio Mane was included in the list of selling players. there is no choice for Mane, even though in fact he could have stayed because he is still under contract until 2025.