Why is the Earthly world considered a good place for Self-realization, and how does this relate to the problem of greed?

The source material explains that while other realms exist, the vision of the Self there is often unclear. According to Chapter 17, the Earthly world (Bhuloka) is specifically desired by those craving Self-realization because it is here that "purity of heart occurs, and the intellect becomes clear like a mirror." This purity is the exact opposite of a mind clouded by greed. The text further explains that a mind obsessed with wealth and worldly objects is "distracted" and cannot receive a Guru's teachings, making it impossible to achieve the clear intellect needed to reflect the Self. Thus, overcoming greed is a prerequisite for achieving the purity of heart necessary for realization on Earth.