Google for the basic aerodynamic and control theory answers of wings.
Could have been turbulence from ground based items/structures, but to conclude the initial dip was from wake turbulence of the lead airplanes is unwarranted due to the wind conditions. Am sure there are some weather history websites that would have the atmospheric conditions to the hour. For this reason, am leaning toward the left wing drop as being an artifact of the mechanical failure.
Whatever the cause, Leeward did an excellent job of arresting the left roll with the right amount of finesse. Reflexes like a cat from muscle and experience memory developed over the years. If nothing else, he can be remembered for his skill.