I'm told not to speculate, but I'm going to do it anyway because this video clearly shows there was an issue going to full thrust. It's an extremely rare dual engine failure or pilots' error not calling up full thrust to keep it flying. Very possible this is the famous bird strike issue Capt. Sullenburger experienced in 2009.
But doesn't seem like a bird strike issue here, right? And given the rarity of a dual engine failure, seems to point to not calling up full thrust? But seems to me that this kind of error would be more common without any technical safeguards?
It's interesting that up to about 30s in the video you can see the plane climbing normally, then it loses power and starts falling, about 10s after take off.
Apparently the pilot radioed "Mayday…no thrust, losing power, unable to lift!” 11 secs after takeoff.
It would seem to fit with a bird strike on both engines. Or contaminated fuel I guess. The stuff about flaps seems irrelevant.
Quite likely this and Jeju Air crash in Korea and Sully landing in the Hudson were all caused by bird strike taking out both engines.
It looks like it was fast enough that most people on board probably didn't realize they were about to crash, or they crashed within seconds of the realization. As torturous as that must have been, it was thankfully very very brief.