As bad as things were for Delaunay-Belleville in 1946, they were even worse for many of the German manufacturers.Some concerns that had still been going before the war - Adler, Stoewer, Horch, Wanderer, Hanomag - would not be back. Long-established Stoewer, like Mercedes, faced a destroyed factory. Unlike Mercedes, Stoewer had been in such a long decline that there was no way to rebuild. And that was that.
One of the last Stoewers - a 1939 Arkona:

Adler made a few cars after the war but basically abdicated. They had no money or materials for cars and there were no buyers anyway. So they made motorcycles and typewriters and eventually just typewriters. Today what remains of the Adler company is a real estate agency.
This Adler Truck, which is pre-war, would've been typical of the few vehicles produced after the war - hardly any of which were ever sold to the public.

Hanomag had introduced a genuinely great car in 1939 - the little 1300 Autobahn sedan:

There was no way to get it back into production, so Hanomag stuck to making heavy trucks after the war, to much success into the 1970's.
Hanomag's larger car, the stunningly well-proportioned Sturm, was dead too. This one was a 1938 model:

They would be back with one final fling at a car - the Hanomag Partner in 1951 - who's design was in the works in the late forties.

The little Partner, which debuted at Frankfurt in 1951, was powered by a 700-cc two stroke, but never reached production.
The old Horch/Audi factory was now in the occupied East, and (like all Auto-Union plants) it was nationalized in 1945. The pre-war Horches were not coming back, so the factory built trucks and a car called the I.F.A.
The original IFA was little more than a 1939 DKW, with a two-stroke twin, exactly what the parent company was producing to the west.

Later on, still connected to the original Auto-Union, they produced the F9, a version of the post-war DKW.

Production of these cars was later transferred to Eisenach, which relates to the BMW story.
BMW also found itself split in two, with the Eisenach factory being nationalizd and procuding modified BMW 327/328 models of pre-war design. These became "E.M.W." until the BMW of West Germany sued to have the name (and badge) removed. The EMW badge was identical to the BMW badge except that the blue parts were changed to red.

This is a slightly later EMW, the most common style was the four-door, but many EMW 327/328 cabriolets and coupes were built as well, and they were identical in every way to a pre-war BMW. They were probably the best cars anybody behind the sloly descending Iron Curtain would get for many years, a least the best out of Eastern Germany.
The EMW and IFA were killed off, ultimately, in favor of the Wartburg - which became Eisenach's definining post-war product.
At Zwickau thing weren't looking that bad after the war, and the Horch eventually returned in 1956 - but Auto-Union, by then having severed connections, prevented them from using the Horch name and the car became the Sachsenring.

The Sachsenring resembled a Humber Hawk and was probably just as nice, but it never took off and luxury cars were not in keeping with the realities of East German life. Higher ups used Russian cars now. So it had a short life - just three years, from 1956 to 1959. In that final year both it and the Zwickau compact were both killed off in favor of the Trabant, which became the most famous (infamous?) product of Zwickau in the post-war years.
With all Auto-Union plants nationalized by the occupying forces, there was, in effect, no actual management at Auto-Union. Wanderer, Audi, and Horch were dumped likely because the people in charge could see no point in bringing them back for a nonexistant buying public.
The Borgward-Hansa group, hit hard by the war, was not yet back in 1946.
Mercedes was rebuilding - already turning out small numbers of pre-war designs virtually built by hand while the factories were rebuilt from total devostation. Opel and Ford faced similar problems but they had the corporate muscle to get back to business because of their American connections.