Contact with residue found on plates or cutlery after washing them has been talked about on the forum several times and several studies have been posted about it. Surfactants in dishwasher soaps are extremely potent, even in small amounts.
In 2013 I suggested on the forum that people should be put on EN, if only to avoid contact with residue of detergents, regardless of the merits of the theory. However, I was not aware that tolerance for EN among adults was low, I was not even of age back then.
CD patients using EN generally don't come into contact with this residue, people in developing countries where rates of CD are low have (or at least had) less access to these commercial cleaning products, and it would explain familial clustering because everyone in the household is exposed to the same cleaning products.
I still don't know what to think of this theory, we can only hope it's this simple.