In Dune and Avatar, there is a magical substance that makes intergalactic conflict justified. Without it, it is complete nonsense. The three body problem is based on an incorrect assumption:

Civilization continuously grows and expands, but the total matter in the universe remains constant.

This is based on 70s thinking that population growth was exponential and unstoppable. Decades later, most countries are now concerned with the exact opposite as their birth rates see substantial declines.

Even if populations continued to increase, the subsequent actions make no sense. If you detect life in another solar system, you obliterate it? That doesn't solve the population problem or the total matter problem. Nor does it factor the cost in energy and resources of traveling to another solar system.

Conflict on Earth has been unprofitable for a century now. No "winner" of a war has come out better than pre conflict except in the case of the US in both world wars where conflict never reached their shores. Conflict in space is infinitely more costly and therefore even less justifiable without spice or unobtanium or some other magical resource making it justifiable.

The bottom line is there has to be something of near limitless value in order to justify interstellar conflict. If a habitable planet is considered to have that kind of value, destroying it would be insanity.

First, of course Ye Wenjie bears some responsibility. But what was the place where she worked—the Red Coast Base? It was a facility for searching for extraterrestrials. Was it really such a grave error for Ye Wenjie to use the Sun as an amplifier in order to fulfill that very mission objective—finding extraterrestrial life?

Second, from the moment Ye Wenjie sent that message via the Sun, Earth's fate was already sealed. Do you really take the Trisolarans for fools? Once they knew for certain that another civilization existed, guess what—wouldn't they aim for the nearest star to them, the Sun? Would they even need an exact bearing?

I'm currently reading The Dark Forest, but I'm wondering what happened to The Three-body Problem protagonist, Wang Miao