That train did not derail at all. The bridge collapsed, or was collapsed and the train couldn’t stop before reaching the bridge. Those trains cannot stop quickly. If they tried to stop quickly it would derail itself by virtue of inertia.
“The bridge collapsed, or was collapsed and the train couldn’t stop before reaching the bridge”
I think bridge collapsed as train was crossing. If it was already down before train got there then engine (typically on front of train) should be in water, I don’t see that here.
It seems odd that the locomotive engines got over the bridge and it collapsed under the tank cars.
If it collapsed when the train first hit it there would be locomotives in the water, not tank cars..