Arsenal failed to win the Premier League because they could not maintain their consistency. I think the reason is that they don't really have the proper preparation and they don't have a lot of options to rotate players, so fatigue and injury became a big problem for them. Besides that, Arsenal also don't really have a winning mentality, one important thing that their rival (Man City) has.
The fact that Arsenal did not win the Premier League really does not disappoint many people. At the midpoint of the season, Arsenal's play ceased to be consistent once more, and after the heat, they returned with the goal of taking the title. The victory over Manchester City by Arsenal was unexpected, and Arsenal truly does not have a mindset of winning.
Arsenal had failed to maintain their consistency due to injuries and most likely fatigue too as the same players were the ones playing all the time. But I don’t really get what you meant by Arsenal not having a winning mentality. I think they’ve got a winning mentality and that’s why they had been leading the league table for a while.
They had been winning their games and gathered some good points to be a bit ahead. That’s a winning mentality in my book. They had suffered some set back and lost points which led to Manchester City who was hot at their heels overtake them and finally win the league. Manchester City no doubt has a winning mentality and is a superb team.
Injuries have a way of tipping the balance of the team because they will undoubtedly affect some crucial positions, which will change the way the team is structured. Additionally, because Arsenal lacked a winning mentality, their performance plummeted when they were expected to accumulate more points, which is when they started losing. I pray Arsenal performs better since they have tested glory they will want to do better next season.