However, maybe Mbappe just needs some more time for adoption to be a good leader for his team.
Good leader? I don't think Mbappe will be a good leader because he looks a bit individualistic. I think there should another player in Real Madrid who can be better to be the captain or leader. In the future, I think Bellingham looks better because he has a nice characteristic.
Obviously, no one knows for sure.
As time goes by, each player will find his identity at the club. There is even a possibility that he could become captain. However if I could choose, of course I would prefer Valverde or Bellingham to be captain because these two players are clearly much more mature and have leadership qualities on the field. Mbappe is better off focusing as a goal hungry striker.