It's even dumber because most life on earth (and presumably in the universe) is single-celled. They generally reproduce so quickly that you'd make up that 50% culling in less time than the fucking movie takes.

Never understood if you could snap half the life away, why not just double the resources or improve the efficiency of existing resource utilization?

Because he doesn't actually care about any of that, he just wants to prove that his original plan would have worked.

So when Thanos was younger, his planet was faced with overpopulation. He proposed that half the population should be killed at random, so that the other half could have all the resources. Of course, he was called crazy, but the planet ended up dying of overpopulation anyway, which convinced Thanos that he was right all along.

So his whole reason for comitting mass genocide is all so he can point and say, "See, I was right!"

Thanos is called "The Mad Titan" after all.

I'm sure I'll be easily shown to be wrong, but I assumed that it's because the universe's mass is finite and that the all-powerful infinity stones only freely manipulate the substance of the universe, and therefore work with limited material. In that case, doubling resources in one place means repurposing equivalent mass from other areas.

The other problem is how you implement this solution across the universe: do you re-engineering biological systems to be twice as efficient? Do you double the input energy? What about non-biological resources: do you speed up geologic processes? Do you simply increase the size and mass of each world and assume twice the resources are available and accessible? How deep of an understanding of each ecosystem is needed to account for all potential target populations, and can a single mind hold all that information in place while giving the infinity stones such a command?

Most pertinently, Thanos was a cynic. He didn't trust any higher lifeform to not ultimately be shortsighted and selfish, and so his brute force solution was a culling.

Or simply make all life half the size.

Could you imagine Earth if everything alive were like, 10% of its size? There would be so much space, so much room for resources to flourish.

So much distance between one country on one side of the planet and a country on the other side that wars between the two would be completely unfeasible.

I uh... don't think I've seen anything Marvel since then so I guess it feels more recent than it is lol.