TBF there is a very slow moving pendulum. The manufacturers screwed the dealerships many decades ago, so the government passed laws to protect dealerships (see also: in some states you can't buy a Tesla at a Tesla showroom). The dealers in turn used those regulations as leverage against the manufacturers.

General speaking: in times of high-margins, manufacturers want to kill the dealerships to capture a larger slice of those margins. In times of low-margins (even negative net margins) the manufacturers want to force the dealerships to eat as much of the cost as possible.