They haven't been duped. At least not in the same way. Russia has no real influence over them. It's an enemy of my enemy thing. The United States has been trending heavily undemocratic for the last 50+ years minimum. And they don't want that to change. Their complaint is that they aren't the ones in charge. They DON'T want to make things better. They just want to be the ones hurting those that disagree. And the only way they can do that is to make things worse. To the point of collapse.
It's just goals aligning. Not some big conspiracy. Or brainwashing. Republicans, Russians, Chinese, and ML all see themselves benefiting from collapse.