What you're forgetting is radioactive underpants were considered kooky even in their time - these were the homeopaths and creationists of their time. I don't think our common-sense beliefs as humans haven't changed as radically as you might think over the past thousand years. I'd bathe in a filthy river if the alternative was just not bathing ever. I can see why people did it. I'd tolerate streets full of manure if it'd mean we didn't have to walk for days between towns. These things aren't ideal, but not crazy, just humans living in difficult circumstances.
"Kooky" is a matter of perspective... the fact is that the use of various radioactive elements in a number of consumer products was a common and pervasive issue.
Hell even dentures had uranium in them until relatively recently, for a 'more natural glow', don't you know. Homeopathy is kooky, but that doesn't stop more people from using it now than were alive just a few hundred years ago. It's kooky, but it's also very popular.
