Adams did a lot of work for the US Government, including many photographs of the National Parks, many of which are in the National Archives and available to the public, but their contemporaneous usage would have given him lots of free publicity. Adams was also very politically active in terms of protecting the environment and our wilderness areas--he met with Pres. Regan regarding his dislike for Secy of the Interior Watts, and Adams declared Regan opaque--"incapable of transmitting light in either direction." Regan though if Adams met Regan his charm would get Ansel to back off--it didn't work.
Ansel worked in a lot of different arenas from nature to commercial, whereas Mortenson seemed to just be working in one area. That probably offered a greater chance for exposure to the public and fame.
Adams's professional career continued through WWII, and the US grew to an adult aesthetic during the war years, and Ansel's style probably fit the new aesthetic better. The Wikipedia article on Mortensen explains a lot in just a few words: https://en.wikipedia.org/wiki/William_Mortensen
Apparently Adams appreciated Mortensen's technique, just didn't like his subject matters and the way it was applied.