Strange indeed - this will have the experts stumped for some time; backups plenty, no gear, no flaps.....
It could be totally unrelated but maybe the “birds” were these:
https://www.bbc.com/news/articles/cvgw8vq2xxyo
The bird strike had to have occurred at an altitude and distance from the airport that would have been before the flaps and landing gear was down. Typically a couple of miles before landing. The only explanation was that the plane was put into a descent mode on the flight director (which is liked directly to the autopilot) and allowed to crash.
The 737-800 is sophisticated enough to follow the ILS to a spot near the beginning of the runway. If the landing gear and flaps were down and the spoilers were armed, the aircraft would nearly land itself, only requiring the thrust reversers to be actuated manually and brakes applied.
For these reasons, I believe that one or both pilots were dead and the plane as deliberately allowed to crash.
I am thinking complete HYDRAULIC FAILURE.