Something that many people do not understand is that an aircraft “stall” has nothing to do with the engine or propeller except possibly as a contributing factor.
A stall in aircraft parlance refers to a change in airflow over the wings or control surfaces that causes the sudden or progressive loss of aerodynamic lift. This is an effect caused by the surface moving through the air at an excessive angle, so that the air stops flowing smoothly over the lifting surface, instead breaking down into a chaotic flow.
Stalls typically happen at low speeds, where an aircraft is pitching up excessively, but can also happen at higher speeds in steep turns or other maneuvers where the g forces on an aircraft make the wings have to support multiple times their normal load.
A midair collision with a small object is unlikely to cause a stall, unless it were to provoke a secondary reaction by the pilot or the control surfaces directly.
Either way, in this case the aircraft in question had the bomber in a blind spot and probably could not see the danger of collision, and in fact may have been frantically looking for it, even lowering the nose to get better visibility, having lost sight of it in a slightly distracted moment.
AFAIK there is no evidence of any condition here aside from inadequate planning, inadequate separation, and pilot error.
As a pilot I am only too aware of the possibility for this kind of accident to occur when operating in the vicinity of other aircraft. It’s surprisingly easy to collide with other aircraft despite the huge amount of empty space lol around you.
It usually takes a few confounding factors to line up to cause disasters to occur in aviation… it’s almost never just one or two.