Their dealers have practically no leverage, or am I missing something?

Their exclusive sales distribution channel has no leverage?

Dealers have been going through a process of consolidation to the point that one group or company owns many dealerships across multiple brands. Autonation has gotten so big it's a public company.

As soon as one OEM tries to rebel, the dealers will tighten the screws across all their sales outlets, relying on their other OEM properties to carry them through. Dealers have all the leverage.

Tesla was only able to do it because they had no legacy distribution network they had to keep alive or else risk their board finding a new CEO.

I've seen this kind of consolidation for "foreign" brands (French + Korean/Japanese), but I think most BMW (+ Mini) and MB (+ Smart) dealers are still pretty exclusive, as well as VW (+ Skoda + Audi), which all belong to the same umbrella company. A dealer chain can switch OEMs, but it's not so much a switch as a complete tear down and rebuild of the business. Sometimes even the dealer's buildings reflect the OEM's brand, not just through signage and colors, but architectonically.

Many dealers, such as AutoNation, sell multiple brands of car. It is much easier for the dealer to decide to push, say, Porsche over Mercedes than it is for Mercedes to replace the dealer.

Mercedes really can't afford to piss off these dealers.

OK, so it seems to be different in the US; I've been thinking about the situation in Germany, where at least for domestic brands, dealers are pretty much exclusive.