I am speculating, but this seems intuitive to me:
Whenever a new player joins the system, elo is created.
As that player loses games, their freshly created elo is split among remaining active competitors. ‘Team’ is a format, more than individual, in which a player who does not intend to play the game regularly is likely to show up and briefly participate.
This is because their friends ask them to.
Those players join (creating elo), lose more than they win (not true about all of them, but as an index), and then stop playing.
Since they have stopped playing, they create a bottom husk of inactive accounts, but the elo that they have lost was still passed on to active participants.