Aren't the engine pylons attached to the wing with shear bolts to allow them to break away at impact?
That's the general idea - you want to lose engines behind since they could be a source of ignition.
The idea is to make the wing box and its fuel tanks not be overloaded by the impact moment forces on the nacelle/pylons when it digs in.
Priceless jewels of wisdom. It would be good to remember these the next time an airliner is depicted flying through solid objects. Thank you.
