The galvanic isolator shouldn't have anything to do with preventing the short from tripping the breaker.

I'm curious enough I sent this thread to Charlie Wing that wrote the book I refer to. He loves stuff like this, and he's a good friend.

I'll see if he has any thoughts on why your mast short, didn't short. Thanks Steve, I'll check my bonding layout as soon as it gets above freezing.

This has been interesting. I don't worry about stray current corrosion problems that come from outside the hull on my boat because I'm so rarely on a dock(1-2 times in 10 years) for any length of time. I don't have AC onboard either. But I hadn't given much thought to stray current inside the boat. I may in fact unbond a few extraneous through hulls and pay attention to the bigger parts and their wiring and connections after your experience. Thanks.