In Avengers: Infinity War, Thanos states his goals plainly. He wishes to reduce the population of the universe in order to create prosperity, reduce war, and so give peace and happiness to the whole universe. He sits back after battling the Avengers, satisfied that his goal has been accomplished. Around him is a universe of peace.
This is not a new idea. It is not the stuff of comic book fantasy. No writer invented the concept as a unique expression of a protagonist’s principle of operation. For the past roughly 250 years the idea has been floated. It is also mainstream in many circles, both popular and and elite, academic and political. An introduction may be read here.
Positive checks to population growth are things that may shorten the average lifespan, such as disease, warfare, famine, and poor living and working environments. According to Malthus, eventually these positive checks would result in a Malthusian catastrophe (also sometimes called a Malthusian crisis), which is a forced return of a population to basic survival.
Thanos’ proposal is in line with the positive checks of Malthus.
The principle is that the world, the universe, is over-populated. If we could reduce the numbers then we would have peace and prosperity.
If it is of interest, Forbes raised this same question. The People’s Republic of China uses forced abortion to control the population, thus managing the prosperity (among other things) of its people. Thanos could simply speak things out of existence. The PROC uses forceps and scalpels. If the idea of tying abortion to this question seems absurd, just look of some of Sanger’s original flyers. She made use of Malthus on population to make her point on birth control. That is, population management. Abortion is simply a mechanism of management.
It seems fair to say that Thanos is a progressive. Perhaps his name should have instead been Thanatos.