This Zohar states that people are blocked in their mind because they only see the MATERIAL ASPECTS of this WORLD and they don't see the spirituals aspects of matters. Therefore constantly pursuing the physical and become blocked from the light. This leads them to accumulate more and more - only to de-accumulate latter in life and can't wait to discard all the physical items they have accumulated.
We recite this Psalm at a mourners' house to remind us of the futility of accumulating material things like the Weasel. How did the Psalmist know?