It almost looks like some kind of incapacitation, and that the PF “lost it” for a bit. Agree about the lack of an announced takeover being contributory; it’s difficult to work out who was doing what for a while but I suspect the PF still had the thrust levers even though the PM was providing much of the pitch/roll input. Aeroplanes can be operated multi-pilot but most of them are designed for only one person at a time on the flying controls.
There may be more revelations that change the look of it but at the moment it doesn’t appear to be their finest hour...