[anotherman554]

It's my understanding that there are two different factions, Machines and Androids. The Machines were built by aliens and the Androids were build by humans.

I don't remember anything in the game about Machines rebuilding YoRHa. Did you mean Androids rebuilding YoRHA?

I don't remember anything suggesting this has been "literally" an endless cycle, in fact I believe they say the aliens were only killed 600 years before the events of the game. (Specifically the YoRHA commander says nobody has seen the aliens in 600 years and then the main characters find the corpses of the aliens and Adam says he killed them.)

So absent any further plot twists (and I don't recall any) the events of the game would have to be at least a bit different from previous cycles before 600 years in the past, and I don't believe there's a suggestion that the exact events of the game ever happened before.

I googled this very quickly and don't see any consensus that your interpretation is correct, but my search was hardly thorough.

[brobinson]

One of the revelations from the machine AIs (red girls) is that they intentionally kept an opponent around to force their continued evolution (referenced in Jackass' report [1]). IIRC they also knew about (or installed?) the backdoor in The Bunker.

[1] https://nier.fandom.com/wiki/Machine_Research_Report

[setr]

>that they intentionally kept an opponent around to force their continued evolution

I don't remember the details of the plot well, but from that report, it's more:

1. Assigned goal: Defeat Enemy

2. Defeats enemy, but realizes that if it's fully defeated, they can no longer fulfill their goal

3. Keeps the enemy alive, so they can have an enemy to defeat. But they're stuck with a contradiction

4. Start corrupting the network to force evolution, to find a solution

That is, keeping YoRHa alive and fighting is independent of the evolutionary task -- it's a side-goal, to fulfill their base requirement (Defeat the Enemy). Keeping YoRHa around is necessary for the android's continued existence, and really all it's for.

The evolutionary task is a search to find a way to get out of this current state (endless war; contradictory/nonsensical setup).