The most important variable for poisoning the world and getting away with it is a regulatory structure that does not require the maker of a synthetic chemical to test it for safety prior to sale and release and puts the burden of proof for establishing hazards on the government and the public.
That pretty much describes the regulatory structure in the United States—with the exception of drugs, food additives and pesticides—until 2016 when the Toxic Substances Control Act was updated. In Europe a similar state of affairs prevailed until the advent of REACH (for registration, evaluation, authorisation and restriction of chemicals) in 2007.
To understand what happens to public health when this is the case, EcoWatch provides an excellent long-form piece on the history of Teflon and its toxic legacy to this day. Spoiler alert: The makers of Teflon knew almost from the beginning about the toxicity of the processes and chemicals used in making it and even today are creating new versions of similar chemicals (after the old ones were discontinued due to liability) and putting them into the environment all over again. The manufacturers made and sold these products for decades, enjoyed huge profits and only now are having to answer for it. The people who owned and led those manufacturers during their heyday and therefore benefited the most financially are long gone. They essentially poisoned the world and got away with it.