The "settlement" sounds very much like City admitting they haven't got a case and the PL promising not to gloat about it. Probably a bit of City agreeing to pay some/all of City's legal costs too
https://www.bbc.co.uk/sport/football/articles/cy7pk8xyy7go
This gives the real reason - basically City want the ability to go ahead with a new Etihad deal
https://www.thetimes.com/sport/football/article/premier-league-manchester-city-sponsorship-legal-apt-lj9hdvpld
The irony is that the means the Etihad deal will be probably now be allowed as it'll be judged at "fair market value" for a team that's been the most successful English team of the last 15 years.
The case to prove that they cheated like f*** to get into that position is still ongoing.