They're materialists who are never satisfied, and projecting their own hedonistic desires onto the rest of the population, they correctly project that it is not sustainable for every human on earth to pursue the same decadent lifestyle that they do. So to keep enough resources to themselves and their friends, they preach a godless version of minimalist spirituality (you will own nothing and be happy) to convince everyone else to be happy with less. They don't intend to pursue that philosophy of course.