Don't think there's any big reason to it, just naturally reached the end of a cycle - the isn't a sporting team in history this hasn't happened to. But in the PL where it is very competitive from top to bottom and they have excelled season on season a big drop off was more inevitable than some people anticipated at some point. Don't think their recruitment has been great in recent times either which doesn't help the 'rebuild'....Remember when we were the only team who could beat them each season (with quick counter attacks). Feels like half the teams in the league can now counter attack well. I wonder how much is City performing at a much lower level or teams just setting up better against them now?