Hey dickholsters! we first need to make sure that we are all talking about the same thing, so a common definition of NPC should be the first thing we do.
I think the 4chan definition is the best. NPCs are people without inner monologe and the abilitiy of visualizing things in their mind.
That's a whole different thing.
NPCs are people who hold opinions, facts, narratives and vocalise them with absolute certainty. Yet lack any background knowledge or information for why they hold that opinion. They have adopted it completely uncritically. Often very passionately. Yet as they just have the opinion. They can instantly swap it out with a different opinion, often completely contradictory and logically inconsistent. They didn't know why they had the previous opinion, they don't know why they have the current one. As they aren't thinking, they seem to not even notice the contradiction or change in opinion. It's just the opinion to have.
They can strongly hold many opinions which are logically inconsistent and not realise it.
They don't like to be challenged on any of this, because it creates strong emotional stress. As they don't know why they think what they think. When pushed to critically think, when asked questions, asked to explain or have contradictions in their opinions pointed out. They have nothing. They literally can't think about these opinions because they know so little about them. Which creates immense frustration. They just KNOW what they think is correct.
This happens on all sides of politics and is probably fed by whatever information bubbles they're in. They are just the correct opinion to have.
It's the difference between, someone having a bunch of information and reasons why they hold an opinion. Versus just having an opinion.
So they can't be talked or reasoned to. It is often highlighted by claims that people just need to "listen." Or telling others to do the research, because they can't explain why they think what they know. They only want to be around people who also just uncritically have the same opinion. Say the same things. Never question it. Just repeat the correct things to say. Like an NPC in a video game.
It's worth noting, that everyone can be an NPC on certain topics, opinions and facts.
In general, it's used to refer to people who are highly passionate and outspoken about political and social issues. Yet are just spouting what they believe are the correct opinions to have. Often for virtue signalling reasons. If you don't agree or question it, it's a sign of being a bad person. Especially for the woke left's version of it. These are the opinions a good person has. As they didn't come to the opinions themselves, they don't understand how someone could not hold that opinion.
Or that is roughly how I see it.
EDIT: This has always been a thing. Whatever the mechanism that feeds people NPC opinions, it has been amplified with social media and the current culture in general. So people have more NPC opinions about things than ever before.