While having "proper" grounding probably saves a lot of boats and their crews, I have heard about emergency back-up GPS units and portable computers inside grounded "oven" even metal aluminum Zeroburton cases with and without ground clips that have those units "fried".

I think the magnitude of the overvoltage discharges, the EMF of the micro discharge and the biproduct of such causes very weird and seemingly selective damage.

These range from one instrument issues -- to wide spread havoc.

There are probably micro discharges that cause problems that you never notice. I had a B&G masthead wind sensor's board "killed". They subsequently replaced the non-conductive arm on the wind unit with a carbon fiber piece. It supposedly protects the unit better by leading the micro discharges elsewhere. Over the last twenty years, that problem hasn't happened again. But that doesn't mean it's not a bit of "luck" vs. otherwise. (Knock on wood -- or, in this case, carbon fiber.)

If you'd been through what you know is a severe lightning storm with strikes all around. I would suspect that you've had "sub-clinical' discharges that pass harmlessly through your system to the water. But that's just my speculation.

Carbon fiber masts (like the one I have), as well as metal ones, can have damage resulting from a direct strike. In the case of carbon fiber, I'm not sure how you are really sure that the structural integrity isn't affected by super heating as it conducts the strike to (or from) the water.