The dangers of lead were known before leaded gas was even invented much less popularized. But immediate profits and convenience are much stronger human motivators than long term health consequences ever are.
See also PFOA and similar. Health impacts were known for 20+ years but it was too profitable so those reports were buried and lobbied against. And consumers weren't eager to acknowledge their amazingly convenient non-stick pans were directly poisoning hundreds of people and causing long-term issues in thousands more.
Now gas stoves are a little bit more unique in that the proponents aren't profit hungry corporations doing shadowy bribery but instead countless chefs who prefer it and will demand it, consequences to themselves be damned.
