JJFCC
Why did the autopilot then auto-thrust disengaged ?
Probably (and it is sorta unclear from the wording of the report) the turbulence caused the AP to drop out.
If the AP can not hold the plane level it gives up and hands the plane to a (presumably more qualified) human. From the brief wording of the report, it sounds like that's why the AP dropped out... Then the PF did some rather odd things.