The guy who put lead in it (Thomas Midgley), came up with a few solutions. Ethanol was actually the better additive for the task (stopping engine knock), but General Motors couldn’t patent the use of ethanol so they ended up going with lead.
Midgley even knew lead poisoning was dangerous and had poisoned himself by accident previously. Much like climate change, the companies didn’t care.
Blame him for selling it as safe, but the real blame lays with General Motors and capitalism for wanting to make sure only they could profit off of the solution.
After working at General Motors he'd go on to bring safe refrigeration to the world by finding a safe replacement for previous refrigerants, ammonia and propane. Decades later, we'd find out that his CFCs were destroying the ozone layer.
Dude basically had the worst effect on the atmosphere ever brought on by a single person.