His head isn't at City, and hasn't been for 12 month in my opinion.
I personally think he felt hard done by seeing everyone around him get big contract renewals whilst he stayed on around 100k a week. Aaron Ramsdale, Onana, Martinez, Pickford and Allison all earn more than him.
Ortega only earns £10m less than him.
The icing on the cake which tipped him in my opinion was when Ortega made the save at Spurs and everyone in the media and socials were saying Ortega won us the league.
It's about lack of principle and recognised value to the team with him I reckon.