How Mortals Could Research But Will Always Choose Not To

 If you pick low-hanging fruit, you grow. Get taller. Relative to you, the tree is shorter, and new fruit comes into the money. 

 First problem: truth is all one thing. You do have to pick all the fruit if you want to grow. Not optional.
 Second problem: mortals love lies and hate the truth. They are not willing to pick all the fruit. 

 You will never run out of low-hanging fruit, but you will very quickly run out of easy fruit with market demand. The failure to [discover] these truths stunts the growth of the mortals, ensuring the next tier of fruit is forever beyond their reach. 

 Or rather, mortals are already dead. Growth is impossible. Therefore they love lies, therefore they don't eat the fruit, therefore they are stunted, which is where we started. Truth really is all one thing. This chain of causation is all a single link, but viewed at different angles.