So Thanos' motivation was to "save" the universe for about 50 years?

Earth's population was about 3 billion in 1960. Now it's over 7.5 billion. So even with Thanos' finger-snap wiping out half of all life on Earth, the population will double again in about 50 years.

So what exactly was Thanos' motivation for killing half of the universe? To "save" the universe for about 50 years?