I don't know, it actually seems to raise more questions, for me :-)
I find it difficult to imagine how a "broach" that dipped the boom - presumably vanged or prevented to the rail, perhaps? - would alone cause the failure of the hull to deck joint on a boat like a Union 36...
It is - to me - a riddle.
Even if the boom was vanged or prevented to the toe rail how does that damage the hull to deck joint?
If the connection was though-bolted I don't see how it could damage the joint...perhaps rip out/break the fasteners with some limited hole damage. Through-bolting provides a clamping force to the joint. Was the stress such that the torque caused the hull side or decking to splinter?
If the connection was not through-bolted why did the hull to deck joint get damaged before the fasteners rip out?
Why didn't the boom bend/boom connection fail/sail rip or the loaded shrouds give before hull damage occurred?
Was the damaged location accessible and carefully evaluated? What damage control efforts were used (plug/putty/tape etc) and were they successful or partially successful?
Once the vang/preventer tore out what kept the boom from hitting the shrouds and damaging the rigging? What actions did Eric take and how successful does he think they were?
Finally - in retrospect - what should have been done differently? What changes would be recommended to avoid a similar event...In setup? In design? In seamanship or watchstandng? In damage control?
Perhaps there are no lessons to be learned...but I doubt it. Every "event" has reasons for its occurrence.
Often the lessons can only be winnowed out by "detached" study of the facts. If the facts aren't available such study can't happen and the lessons are lost.
Perhaps I am wrong but maybe this is Jon's point. And I think it's a good one.