Why on diamond league?

My trophy is around 1100 then i was invited to diamond league. Then players whoop with 30000 medals and players have 4000 trophy. why am i on this league and not the one with same trophy as I am? how to choose the league to join?

You can’t it’s random which player is in the same league as you.

I think you should visit this site to know more about leagues: http://royal-revolt-2.wikia.com/wiki/Leagues