What iron did, or at least was associated with, was a change in military tactics and organization that made the expensive chariot-based forces of the centralized states less workable. But undoubtedly the LBA collapse had other factors, like severe prolonged droughts (which are attested in the archaeological evidence).

This proposed change in tactics happened before iron weapons became widespread, though. Iron should I think be seen as a cope for a world in which long distance trade in tin had shut down.