The firefighting loss was because a huge wing crack went unnoticed until they hit turbulence in and around the fire drop. As you could see in the video, both wings departed the aircraft. You can only bend metal so many times before it breaks.
Many countries operate older 130's that have come out of US service. Whether the props lose a blade or something else catastrophic happens, there is often no trace left to discern the cause if it happens over open ocean. This was mid-Pacific between Kwajelein Island and Hawaii.
We had fried a starter starting up that morning at Kwaj and were lucky enough to get a "BJ" from another 130. We tucked in tight behind his engines and used his prop blast to start our motor. That was a routine op back in the day. The other Herk was a weather bird with an all female weather observer crew. The last thing they asked was, "Will you respect us in the morning?"
Teamwork. It what gets stuff done.