I am still relatively new to this game, but I wondered how we get assigned into a league at the start of a season.

Today was the start of my season 5, and I've noticed everyone in my league is Russian except for myself.

Also last season (level 4), in my league the highest rating was a team with a average rating of about 31, whilst in some other level 4 leagues, there were about 5 teams all with an average rating between 37-42.

Are we assigned randomly or does previous league position and team rating play a factor?

The same question can also be applied to Champions League.