Backstay failure caused forestay failure.. check it out..the stay was pulled out of the swage.
Interesting. Do you have photos?
Typically forestay tension is set at about 12-15% of breaking strength. The swage has to be able to withstand considerably more tension than that. The terminal ends, whether swaged or mechanical are typically almost as strong as the wire itself. if the loss of a backstay caused the swage to fail, then I think the swage was either poorly made or about to fail anyway.
The important story is how the standing rigging is a robust and fragile system that keeps the mast up. Failure in any part of the system can lead to failure of the whole system. For those who leave their masts up, out of sight, out of mind is not a good strategy.
What's the story about how the kingdom was lost for the want of a nail?
Hope your insurance company steps up to the plate and helps you out.