I'm not sure either. I know personally this is the toughest league I've had, and I always start with a 5* team that becomes 6* as the league goes on. For example, from memory 12 out of 14 teams (including me) started with pretty much 5*+ teams this season, which is ridiculously strong. However I feel it still comes down to chance and position from the previous season?
Who knows.
These are the teams In my league
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And this is my league table and me, just to prove they're not random teams

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Maybe you could be on to something?