Mane and Kane are both very similar types of strikers, so it's certainly not because Mane wasn't comfortable in the position and so couldn't be brought into the game properly.
Mane and Kane are not similar, Kane is a striker and Mane is a left winger.
You're right of course, but I'm less concerned with the respective position (you can also have Kane play on the left wing) and more with how Mane and Kane behave on the field. For example, they both go into duels in a very similar way, and the move to the goal when in possession of the ball is also comparable for both players. In my opinion, it will be interesting to see whether the team's playing behavior can be better geared towards Kane or whether he also loses performance.