He admitted it was boring but people wanted more. He then admitted he wanted more. Thus the newer books which were filled with action.
Asimov's words:
“THE STORY BEHIND THE “FOUNDATION”
By ISAAC ASIMOV
The date was August 1, 1941. World War II had been raging for two years. France had fallen, the Battle of Britain had been fought, and the Soviet Union had just been invaded by Nazi Germany. The bombing of Pearl Harbor was four months in the future.
But on that day, with Europe in flames, and the evil shadow of Adolf Hitler apparently falling over all the world, what was chiefly on my mind was a meeting toward which I was hastening.
I was 21 years old, a graduate student in chemistry at Columbia University, and I had been writing science fiction professionally for three years. In that time, I had sold five stories to John Campbell, editor of Astounding, and the fifth story, “Nightfall,” was about to appear in the September 1941 issue of the magazine. I had an appointment to see Mr. Campbell to tell him the plot of a new story I was planning to write, and the catch was that I had no plot in mind, not the trace of one.
I therefore tried a device I sometimes use. I opened a book at random and set[…]”
“Empires. This was to be illuminated by the science of psychohistory, which Campbell and I thrashed out between us.
On August 11, 1941, therefore, I began the story of that interregnum and called it “Foundation.” In it, I described how the psychohistorian, Hari Seldon, established a pair of Foundations at opposite ends of the Universe under such circumstances as to make sure that the forces of history would bring about the second Empire after one thousand years instead of the thirty thousand that would be required otherwise.
The story was submitted on September 8 and, to make sure that Campbell really meant what he said about a series, I ended “Foundation” on a cliff-hanger. Thus, it seemed to me, he would be forced to buy a second story.
However, when I started the second story (on October 24), I found that I had outsmarted myself. I quickly wrote myself into an impasse, and the Foundation series would have died an ignominious death had I not had a conversation with Fred Pohl on November 2 (on the Brooklyn Bridge, as it happened). I don’t remember what Fred actually said, but, whatever it was, it pulled me out of the hole[…]”
“issue. By this time, though, I had grown tired of the Foundation stories so I tried to end them by setting up, and solving, the mystery of the location of the Second Foundation. Campbell would have none of that, however. He forced me to change the ending, and made me promise I would do one more Foundation story.
Well, Campbell was the kind of editor who could not be denied, so I wrote one more Foundation story, vowing to myself that it would be the last. I called it “--And Now You Don’t,” and it appeared as a three-part serial in the November 1949, December 1949, and January 1950 issues of Astounding.
By then, I was on the biochemistry faculty of Boston University School of Medicine, my first book had just been published, and I was determined to move on to new things. I had spent eight years on the Foundation, written nine stories with a total of about 220,000 words. My total earnings for the series came to $3,641 and that seemed enough. The Foundation was over and done with, as far as I was concerned.
In 1950, however, hardcover science fiction was just coming into existence[…]”
Excerpt From: Isaac Asimov. “Foundation.” iBooks.