To reinforce the comments about indeterminism:-
there is nothing in the video as seen (that is, qualitatively) to show that the pilot didn't suffer from indecision or incapacity and let the nose fall through after going knife-edge.
To exclude that possibility, you would have to reconstruct the actual (quantitative) dynamics from measurements of the video, a skill which I don't recommend trying to pick up in the course of a student project assignment.......
What one might assume is that the pilot was highly skilled, well aware, and not able to roll level when the nose starts to fall through, because of some aerodynamic control impediment, for example spoilers not able anymore to generate differential lift on the wings to enable roll. But that is an assumption. You would have to validate it by analysing the true dynamics of the manoeuvre, which is not apparent without considerable reconstructive skill from the video. One might be able to tell from the video if wings-level roll inputs were attempted.
PBL