Because people are annoying AF. Cutting the number of idiots in half was a great move.

Because his original motivation was to impress a girl he liked. Death is a hot chick that he was in to but she wasn't interested in him. So he figured killing half of all life would impress her.

They decided to make his motivation more sympathetic for the movie. They didn't think through how his new goal could be better served with the godlike powers he gets.

He likes killing, and he likes thinking of himself as s benefactor who is just so much smarter than everyone else that he’s the only one who sees the solution, who can rise above petty emotions and do what needs to be done. Sure he’s killing trillions, but only to save them from something worse that would have happened (he reasons).

Most people wouldn’t mind killing someone if there was a moral justification for it and they could get away with it. Just look at how people react to videos of someone stealing a bike: everyone in the thread is ready to literally murder that person. Because they think they have justification. Well, Thanos thinks he has a justification too. And he’s murdered millions up close already - not with a snap - there’s no going back now. In order for his mass murder to be excusable there has to be a larger purpose to it. There has to be.

He’s a knot of different psychoses mixed together. Primarily narcissism plus homicidal tendencies. He’s fully insane, if that did not come across somehow. Totally pinched off from the rest of reality, living in his own self-reinforcing loop. He’s got a lot of power and that makes him more and more immune to reality intruding on his fantasies.

Logic doesn’t come into it. Not only could he have created more resources… he didn’t even think that populations would just grow again and bring everything back to the same place. No he’s blindly playing out the track he’s on. The only way out is forward, because he can’t justify anything behind him otherwise. When the universe isn’t grateful for what he did, and his fantasy of being the benefactor falls apart, notice that he is ready to destroy the entire universe and become god, because how else can he escape the crushing blame for what he’s done.

Back on Titan, Thanos told his people "you need to kill half the population to save our civilization from disaster." The people of Titan dismissed Thanos as insane. Thanos, being actually insane, decided he was going to prove he was right by going around massacring halves of populations.

In other words, he's not doing this to actually help anyone, he's doing it just to prove he was right. Solving the universe's problems by other means wouldn't do that so that's not an acceptable outcome for him.

I love how this whole premise never gets questioned. By anyone. None of the super smartest people in the movie were like, "no that won't work." The premise just gets accepted as true, but it would be bad.

"I'm going to eliminate half of all life in the universe" hey thanos did you know that scarcity in modern society isn't driven by population at all, and is in fact an artificial condition imposed on the lower classes by the ruling class that hoards those resources?

No its just like, "well killing people is wrong but it would probably work, people might be sad though." No Disney, fuck you. Don't let people believe this shit. Thanks for your endless support for cultural fascism, ya fucks

The comic had better writing. Thanos killed half the universe so he could fuck Death. He thought she'd love that shit since she's, y'know, death. I'd do the same for a goth girl.

I think what was missing was his obsession with Death. The MCU didn't include his infatuation and Death's hold on him. He wanted to impress her and she held him to it in the comics.

The short answer is that they had to come up with something more palatable to a movie audience than “I’m evil and have a crush on the literal Lady of Death.”

In the comics, he was trying to impress his girlfriend, Death.

That would have been a boring movie.

"When your only tool is a hammer, everything looks like a nail"

Dude just wasn't very smart

Because it’s a pretty dumb story at its core. Because they wanted the “worst villain” but couldn’t come up with something more interesting or intelligent than “misguided environmental terrorist.”

They don't call him the Sane Titan.

And he's purple because he's an alien who Jim Starlin gave purple skin.

Because the only way Marvel movies know how to ratchet up the stakes is having more and more people die.

same reason expanding the highways doesn't relieve congestion. Induced Demand.

FWIW, he basically did double it. I mean, if you have x resources for a population, and you halve the population... they now have twice the resources...

Comic book universes have never been great on internal consistency. Most technologies and superpowers we see would have ushered in a new golden age for humanity.

On doubling the resources, I think that falls into the "obvious, but wrong, answers contain the word 'just'".

let's say you double the resources. without being specific, you just doubled light and the mass of the sun and the mass of the planet and killed everyone.

ok, let's say you get more specific, drinkable water. double it. in place? there goes every pipe and reservoir on the planet.

plant nutrients? now the concentrations could be toxic for the plants and now they're dead.

double the asteroid belts? a lot of these species are space faring, after all.

each species and planet would need a custom solution, and that takes work. In addition, the main issue isn't the availability of resources, it's how they're allocated.

just doubling all the resources could end all life in the universe.

With all the food we throw away now, it's not a resource peoblem anyway. And that's too much logic for a Disney movie

I think you are thinking to hard about stories that aren't meant to be thought about a lot. Whether you half the population or double the resources it is just a temporary "fix" anyways. It's just a plot device for creating conflict and killing off fan favorites without actually killing off fan favorites in the end.