The families didn't even know that Jones had talked about Sandy Hook for twenty minutes on his 3 hours a day five days a week show until five years after the fact when the ambulance chasers recruited them.
They were so traumatized they didn't even know they had been traumatized until five years after the traumatic event occurred.
You don’t have to know what has been said, at the time it is said, to prove defamation. People sue all the time about things that happened in the past that they weren’t aware of until later.