Gio's tenure coincided with the scum going on a domestic run where they dropped a ridiculously small number of points. People talk about him losing a 4 point lead when he arrived, but when your rivals win every game they play there's not a lot you can do about that.
Similarly why I don't buy too much into the notion that Clement dragged us back into the title race from being 8 points behind. The main reason for this is the scum dropped so many points, on average we've picked up roughly the same number of points as we did under Gio & Beale.
Ultimately, any manager will be judged by where we are in comparison to them and, other than the head to heads, there's not a lot you can do if they go on a huge winning streak - which is where Gio was very unlucky.