Art is sticking with the Clones because He wants to see how it ends.
Art was living comfortable life as police officer when suddenly His deceased partner has an identical twin who also happens to have and so on.

So at this conjunction, Person of Interest changed. 2 and a half season of getting better by the hour, they changed a game plan.
I find this to be the moment The Beatles had after "Help" album,"we gotta change to be relevant".
The death of Carter seems to divide the audience of POI,