The two are not necessarily opposed

If A and B agree on 99% of issues then awesome. But, siding with A means that for the other 1% your choosing A over B.

They represent the corporations but in the case of an autodealer association they are probably claiming to represent their employees. Think of them similar to a union except they are lobbying legislators instead of corporations.

Automotive dealerships are not at all like a union. There's a critical distinction here between labor and capital.

I never said auto dealerships but the autodealer associations in each state. The associations are the ones that are doing the lobbying on behalf of dealers. IIRC Ford tried to do direct sales to customers in the 90s maybe? The Ford dealers lobbied and shut Ford out.