Sometimes it doesn't need to be a team that controls the game to be the winner and Liverpool managed to perfectly beat Arsenal who controlled the game even though some of the players who became the foundation of Liverpool could not strengthen the team, but it didn't really affect their game.
Liverpool again aim at multiple titles in a season but they have to cleverly adjust their main targes and probably have to make decision to sacrifice one or two targets. It will be better if at the season ending, they manage to lift one tropglhy than end as a runner up in two or three competitions.
Losing to Liverpool made Arsenal suffer three consecutive defeats in all competitions, and that's not good enough for Arteta because it will make it even more difficult for them to compete in the title race as well as in the Champions League, because it means there is a problem in terms of them maintaining consistency and Arsenal will be like last season very good at the beginning of the season but slowly they failed in many matches.
Arsenal don't have good performances recently and they are similar to Liverpool, must pick priority for second half of season. Else they will end this season with nothing while their players can get exhausted and injuries. This if happens, will affect their club preparation for a next season as well.
Losing to Liverpool, a strong opponent, is not too bad and if Arsenal can use this defeat to focus more on Premier League, it is not too bad change for them.