split index of tuples into multindex pandas dataframe - using python

I created a dataframe from a list of dataframes like this:

team_df = pd.concat(all_teams, keys=flat_list, axis=0)

I attached a picture of the output.

I want to convert

it to is something like this:

team1

player 1
player 2
player 3
player 4
player 5
player 6

team2

player 1
player 2
player 3
player 4
player 5
player 6