One assumes AF speculated about a lightning strike as a way of explaining the sudden loss of the transponder at altitude.
When will everyone finally understand, that the transponder has no role whatsoever in a non-radar environment?? There're no radars in the middle of the ocean, so it's not interrogated, therefore it's not replying to anyone...
if it was lost while still under radar control, at least there would be an idea where to start the search.