I wonder if he didn't care or if he knew they would keep doing it without him.

According to Bryson's account, he deliberately mislead us about the dangers of tetraethyl lead by making a public demonstration of washing his hands in the chemical. As a chemical engineer he knew a single exposure was not sufficient to cause the lead poisoning that was evident in the workforce at his factory and was counting on a scientifically illiterate public not understanding how toxicity operates in organisms. He was correct on both counts and we can never let the profit motive enter these type of calculations e.g. money in healthcare, oil companies publishing climate science, etc, and expect healthy outcomes.