They already understand the second order questions though. Why would they ask the humans?
They know what's outside their enclosures, they know they're there because the humans want them there, they know strange humans like to see and interact with them through the glass. They just don't care, so long as they have their tribe around with things to do and they get tasty food
Animals understand existence better than humans do. They understand life and death better than we to. Our higher intelligence makes second order questions complicated because we put ourselves through mental gymnastics
We should be asking apes about the meaning of life, not the other way around