This was pre-internet and in remote areas where there is a distrust of central authority.

And there are loads of examples through history up till current day that show that blindly trusting authorities is naive. Heck, even in the article, some doctors were poisoning their patients with iodine. It is not far fetched that some people in these areas were informed of these problems. So a tiny amount kills us... and so you are saying any even tinier amount will save us. I'd be pretty skeptical too.

It seems that when presented well and with personally verifiable evidence, people were willing to accept.

I am really flabbergasted when people blindly accept in mass what authorities tell us.