It was however relevant to the survivability of the accident: if the left engine wouldn't have detached, or would have detached in a more "manageable" way, the other engine (probably the tail engine from how it looks) wouldn't have been affected too, and the pilots would have had a better chance to take off. Plus the whole "when an engine detaches, it shouldn't start a fire in the wing it was attached to" part of course...
Yes, agreed, the secondary safety wasn't there either. There was a Boeing accident near Amsterdam with the plane crashing into an inhabited area, it had dropped two engines but kept flying, at least for a while...
A 747 with 2 engines out that's already got some altitude and speed is much more "survivable" (still extraordinarily difficult) than a trijet trying to take off on 1 engine, which is impossible.
Planes can safely land with 0 engines, though this is obviously "not ideal." See: Gimli Glider.
