Yeah. The suggestion I saw was that instead of retracting the gear they mistakenly retracted the flaps.

Now in the video the wings do look quite flat. But yes, it would be hard to say for sure in a video of that quality at that distance.

The descent looks (to my untrained flight sim eyes) to be controlled albeit without power.

At 400ft agl they had very little options most likely. Not even much choice in what they hit.

Very sad all round.

So the VR speed for a 787 isn't going to be set like a Cessna 172, it's going to be a calculated value depending on weight, temperature, etc. The computers will calculate this speed for you before flight, assuming all info is input correctly.

The cockpit won't be able to see the flaps visually but will have a digital indicator that shows the position. During pre take-off checks one of the procedures would be to check this indicator for the correct setting.

With the very limited available info and the fact that video shows it slowly descending without obvious external mechanical issues, my initial guess is on pilot or computer error.