He paused at this point to consider something. Then he said, "All I know about ancient cultivation is that they could cultivate with some substance in the air, and that substance could increase their lifespan. They seemed to use that substance too much, so it ran out. That made ancient cultivators unable to cultivate, so they had to switch to another method."
He was actually telling the truth about this. This is all he knows about ancient cultivators. If not for the fact that he will need to beg for 500,000 years of lifespan later, he wouldn't have said anything.
He didn't want to offend his sponsors, so instead of lying and saying he didn't know anything about ancient cultivators, he decided to tell them something useful.
Actually, he had started out intending to lie. His decision to tell the truth was made after he said his second sentence.
