You might as well give up trying to figure out lightning's
unpredictable ability to damage things. I had a direct hit on my
longwire years ago and the antenna was indirectly grounded to the ham
transceiver chassis. It still took out the output RF amp but did not
damage the receiver at all. The antenna was totally vaporized and what
was left of the ceramic insulators had the most beautiful copper
plating around the holes! The same strike opened up a buried AC cable
that controlled the yard lighting. That never did work correctly again
and I was too lazy to dig it up for repair. I'm glad your FRG was not
damaged any more than it was. I worked in high voltage physics years
ago and it was facinating.

Frank
Tucson