And yet poor people constantly vote for tax cuts for rich people.

Is that true? One's options are limited if all one can do is vote for representatives, instead of directly voting on an issue themselves.

It's helpful to distinguish between the side-effects coming from one's vote and the intention/motivation for that vote. (This is called the doctrine of double effect.)

I would be surprised if many poor people vote with the intention of giving tax cuts for rich people, instead of voting for a candidate who they feel resonates them for other reasons, where it is an incidental fact that this candidate will push tax cuts for rich people.

This is true and I was being a bit snarky, but let us not forget the story of "Joe the plumber"