In an attempt to show the wider context of the changes in 1940s literature and how they may have affected Campbell and science fiction, let's take a look at Doc Savage, the Shadow, and Babette Rosmond.
The pulps were dying by inches during the Forties and the reading audience, cynical after another World War, was no longer satisfied with pulp fiction and pulp heroes. They wanted more thought, polish and realism in their fiction. Babette Rosmond perceived this and surrounded herself with writers who could meet these new demands. She could hardly get rid of Lester Dent (though Walter Gibson did quit during her tenure), so she juggled his novels to make them less conspicuous and showcased the work of MacDonald and others.
Murray, Will. Writings in Bronze (pp. 45-46). Altus Press. Kindle Edition.(This seems to be less the audience's attitude and more the editors'. In the 1940s, editors had more power over the market than readers. Changes in literature were driven by the fashions of the editors instead of market pressures. In part, this is because the editors were the market for writers. Sales plummeted under Rosmond, but her policies were in line with those of Street & Smith in the 1940s. I'll be looking into those soon. Rather than Rosmond being a child of Campbell's ideas as I previously assumed, it appears that she instead was a child of a new management that squeezed the vitality out of Campbell and the pulps.)
The years 1946 and 1947 were years of change in Doc Savage, and this was due largely to Babette Rosmond and her policies. It’s rumored that Lester Dent didn’t get along with her very well and she, in turn, evinced a cavalier attitude toward his Doc Savage novels. With the May 1945 issue, she shunted the lead novel to the back of the book in much the same manner as a parent locking an idiot child in the cellar. Though she repented that move in April 1945, it became increasingly evident that she thought more of developing her new writing staff than she did of Lester Dent and Doc Savage.
Murray, Will. Writings in Bronze (p. 45). Altus Press. Kindle Edition.This was a few short years after many of Street & Smith's pulpsters were effectively driven out of the career. Street & Smith was looking to make slicks out of their pulps and needed new writers in the current styles to do so. The resistance to the old styles even trickled down to the writers:
In Bronze Shadows #3 (February 1966) John MacDonald related the story of how he was asked to join the ranks of the Kenneth Robesons:
In 1947, Babs Rosmond asked me, very cautiously and tentatively, if I would like to try a Doc Savage. I have the vague memory that Lester Dent was ill at the time. I do remember that I certainly had need of the money. I told her that I would let her know. I got out some of the back copies of the magazine which I had saved because they had contained stories by me. For the first time I read two Doc Savages all the way through. I did some fretting and some pacing and finally phoned Babs at her office at Street & Smith and said that I could not fault them on the basis of action, or moving the people around, but I just could not bring myself to imitate a prose style so wooden, so clumsy, so inadvertently hilarious that it was like a parody of the style you might term Early Comic Book. I said that Doc seemed to me to be a truly great comic figure, and I was sorry to let her down, but… She said she hadn’t really believed that I would do it, and that in fact she would have been a little disappointed in me if I had given it a try, disappointed in me.
Murray, Will. Writings in Bronze (p. 46). Altus Press. Kindle Edition.In 1948, Babette Rosmond would turn away from editing pulps for her own literary career. By then, the damage done by her and Street & Smith's management was permanent. Instead of continuing with the plan to revive their flagging pulp line, yet another management shakeup decided on a different course:
When the end did come, it was as if a sword had fallen. In 1949, the last of the Street & Smith heirs, Gerald Smith, became president of the firm. The sword-wielder is unknown; it may have been Smith or Chairman of the Board, Allen L. Grammer. In any case, it was the latter who announced in April of that year that Street & Smith was dropping Detective Story, Western Story, Doc Savage, and The Shadow—leaving Astounding Science Fiction the sole survivor of a long line of pulps. Citing television and the fact that readers were tired of the pulp format, Grammer said the company was shifting toward the women’s market.
Murray, Will. Writings in Bronze (pp. 49-50). Altus Press. Kindle Edition.