We are discussing about the characteristics of the demons. So they have lost their intelligence. Etam drstim avastabhya nastatmanah alpa-buddhayah. Nastatmanah. Atmanah means spirit soul. So they have lost the sense of spirit soul. They do not know that "I am not this body, I am spirit soul. Aham brahmasmi." So therefore they do not know this. Therefore they are called nastatmanah. They have lost their spiritual sense. Why? Alpa-buddhayah, not very intelligent.
Lectur on Bhagavad-Gita 16.10, Hawaii, 6 February, 1975