Just under what legal theory before the FDA was poisoning people a legitimate business ?
THE RADIUM WATER IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
Back in the U.S. robber-baron era (1870-1905) it used to be the case that it was your own fault if you put it in your mouth. It didn't matter if the seller marketed it as edible despite knowing or suspecting that the product was poisonous (such as radium water or formaldehyde-preserved milk). As the buyer you were supposed to know better, as summarized by the legal doctrine caveat emptor ("let the buyer beware"). It was only later that caveat emptor was _partially_ overturned by the invention of the "implied warranty", as federally formalized in the Uniform Commercial Code of 1952 (though the concept was kicking around decades earlier than that on a state-by-state basis). In the absence of a warranty (explicit or otherwise), the seller had made no promise to the buyer about the product sold, and with no promise to break there was therefore no fraud on the seller's part. No fraud, therefore no wrong and no restitution: no wrongful death damages, no medical bill expenses, not even a "satisfaction or your money back" refund guarantee.
To this day, there's still quite a bit of caveat emptor in the law. For example, cigarette smoke is poisonous at the intended dosage, full stop. Habitual smoking of cigarettes is known to inactivate hemoglobin by way of carbon monoxide, to reduce lung capacity by accumulation of scar tissue, to damage the cardiovascular system by hardening the arterial walls, and to dramatically increase the risk of lung and other cancers. But despite their documented toxicity, to this day tobacco companies are not held liable for selling them. They have been sued several times, but generally for their advertising, and many of the advertising suits have been for ads that played up false benefits or downplayed real drawbacks -- i.e. they made a promise (implied warranty of fitness) that was then broken (fraud). But so long as the buyer is duly warned (no false advertising, the Surgeon General's Warning is present), the situation reverts to caveat emptor and it's again the buyer's own fault if they put poison in their mouth.