Germany is very famously pro-union and boasts a strong auto industry. What did they do differently

The German auto industry is in a world of shit, actually, but I don't think they can blame the unions for that. Their "works council" model is very different from a typical UAW stronghold in the US. The unions (and in many cases the state itself) are active partners in corporate ownership and management, so they have a stronger incentive not to kill the golden goose.

That's a more reasonable take than the person I responded to. They had the lazy anti-union talking points of "they take your dues and you stay poor". Which must be straight out of a Pinkerton handbook from the 1910s or something.