I'm confused by the idea that a 'wise' person's knowledge can actually be ignorance. How is that possible?

Chapter 50 addresses this seeming paradox directly. It clarifies that a person may be considered 'wise' by worldly standards, but if their mind is fundamentally fixed on acquiring wealth and luxury, and they are engrossed in thoughts of their wife and children, their knowledge is superficial. As explained in Chapter 50, such a person is deluded by these attachments and does not truly know their own welfare. The text states that as long as a person is without devotion, their so-called knowledge is covered by ignorance, making them unable to see the path to their own ultimate good.