#2 Their new formation
As mentioned already, Arsenal won their final five Premier league games with a new formation as well as seven of their last eight league games. They also won an FA Cup semi-final and FA Cup final against both Manchester City and Chelsea, two clubs who finished above them in the Premier League table.
The new formation has transformed the performances of their centre-backs and central midfielders. Since changing to a three at the back, Rob Holding, Gabriel Paulista and Nacho Monreal have all performed excellently. In centre midfield, the combination of Granit Xhaka and Aaron Ramsey seems to be working splendidly, as the two players put in man of the match performances in the games at the end of the season, suggesting Arsenal may have found a solid midfield pivot.
The previous 4-2-3-1 set up had seemingly become stale under Wenger. Changing that has given belief to all Arsenal fans and could be one reason why Arsenal might win the Premier League next season.