Why is it a sign of astroturfing and not just hyper political climate?

Well, if broadly popular organic posts net about 100, I would expect organic partisan posts to have a ceiling of +50. Still, more realistically, the net would be about zero because half the people would downvote them.

But, somehow, partisan posts in one direction always seem to net over 1000 or 2000, yet partisan posts in the other direction net about zero.

Even with a skewed distribution, I would only expect maybe +20 to be the ceiling.

> the net would be about zero because half the people would downvote them.

Why would you assume that? It's a fallacy to assume that political opinions are evenly distributed. People seem to agree that different sites attract people of different political persuasions. A post that gets highly upvoted on Truth Social might get highly downvoted on Reddit, and vice versa. That's not astroturfing, that's just self-selecting communities.

> partisan posts in one direction always seem to net over 1000 or 2000, yet partisan posts in the other direction net about zero.

Again, it depends on the audience. This is not a new phenomenon. 50 years ago, you would get a different response to certain political statements depending on whether you made them at a Grateful Dead Concert or at a meeting of the Fraternal Order of Police. Why should today be different?

> I would only expect maybe +20 to be the ceiling.

Why? People feel strongly about their political believes. It's polarizing and engaging in a way that a post about crockpots or guitar strings isn't.