my league had a total of 6 previous league winners, 3 cup winners and 4 CL winners in there, also a few 2nd places in CL and Cup.
If you kept adding people that are on you'r level(same server) and curentlly winning their league, most likely they'll be on your league next season as the engine itself is trying to regroup friends in same league.
What i think is, the engine takes the higes Q player and hten put him as league leader,after that it adds his friends or atleast most of them.
Thats's a good way to make your league more interesting, isnt it -

Idk if you'r complaining or you'r actually happy about it..
Topeleven is a challenge :P