How does a league reputation significantly increase?

I'm currently managing in Scotland, and at the end of the season, I got a mail about the reputation changes in European leagues. Cinch Premiership climbed one spot in the rankings, which is fine, since I did alright with Celtic in the Champions League.

But what surprised me was the Croatian league climbing ten spots. It went from 22nd to 12th in the span of one season. Dinamo Zagreb were in my CL group and they finished 4th. They only got 3 points in a win against Ajax. And I didn't see any other Croatian club do well in European competitions either.

So what happened, I wonder.