Why is it a problem? If they were charging more than MSRP and still move the cars, it means that the market values the cars at a higher rate than MSRP and someone can make money off of the difference - isn't that the whole point of capitalism?

How's that someone get chosen though? Quality of their work? Level of effort they put in? How much money they have? Outright bribes? Threats of violence?

Where car dealerships are passed down from father to son, for generations, and is locally one of the most powerful organizations, to the point that competition is outright prohibited, it's not a free market, which is one of the cornerstones of capitalism.

You open up a competing car dealership on the opposite side of the street and sell for cheaper (assuming that you have access to wholesale prices from the car manufacturer - that is the part that needs to be regulated).