You are half correct.
Civilian versions of Opel Blitz trucks produced between 1930 and 1975 were mostly 2 wheel drive.
The military version of the Opel Blitz 3 ton truck which entered mass production during 1940 was 4 wheel drive. This was Germany's equivalent to the U.S. Army 2 1/2 ton truck.
I know they made 4x4's, but they were a small percentage of total production. Just look at all the film/pics on the Russian front. There are always a long string of 2wd trucks being dragged along by either tanks or haltracks.