Arteta did not go in there with the intent to play bunker ball. This is a Pep trained man after all. What happens was, that at the end of last season and start of this season, Arsenal has 3 successful (as in they got the win) vs Liverpool and City where they set up to absorb pressure and take a chance on opportunistic counters.
I just think he ended up deciding that the play style that got those results vs the two strongest teams in the league was more suited for the squad he currently has.
I don’t think he all of the sudden became Mourinho in philosophy, and I doubt he’ll employ these tactics throughout his career, it just appears that he feels for the time being, with this squad, it’s the best approach.
Whether it is or isn’t is up for debate, but I feel he plays like this because he feels it’s a necessity at this time.