I would add his previous habit of eating a lot of tuna. Mercury poisoning was likely why “mad as a hatter” came to be. Hatters would brighten their pins and needles with dips in quicksilver, to see them better. Holding some pins in the mouth caused ingestion in small amounts that slowly poison. It isn’t a far reach for a person to see their neurologic symptoms of mercury poisoning to be from another mercury source, like the mercury in one particular vaccine.
I would add his previous habit of eating a lot of tuna. Mercury poisoning was likely why “mad as a hatter” came to be. Hatters would brighten their pins and needles with dips in quicksilver, to see them better. Holding some pins in the mouth caused ingestion in small amounts that slowly poison. It isn’t a far reach for a person to see their neurologic symptoms of mercury poisoning to be from another mercury source, like the mercury in one particular vaccine.