Whatever happened in the last 100’ or so, was caused by excess altitude and speed when they started the approach. I believe they were at least 500’ high and 40-50 kts fast. The 777 is very difficult to slow down once you start to descend on the glide path. If you are high and trying to converge or catch up to the profile/visual glide path, you accelerate and then exceed flap speeds. It was an unstabilized approach and should have been abandoned long before reaching the runway environment.
It (777)is just too clean and those 90,000lb thrust engines are still producing some thrust in idle or residual thrust if they are reduced too late.