I believe this myth was spread by radical opponent of Israel, Norman Finkelstein, in his 2000 book, The Holocaust Industry. Notorious Holocaust denier David Irving also spread this myth, although I’m unsure if it originated with him.

However, there were certainly many publications of books and movies about the Holocaust in the 1940s and 1950s, and these indicate widespread public knowledge and interest at the time.

These include the Anne Frank’s Diary of a Young Girl, published in 1946 in Dutch, in 1950 in French and German, and in 1952 in English. A play based on this book won the Pulitzer Prize in 1955, and the 1959 film won several Academy Awards.

Olga Lengyel published her Auschwitz memoir Five Chimneys in 1947, which received positive reviews. In 1949, Leo Schwartz’s The Root and the Bough told 33 first person stories of survival. In 1951, Krystyna Zywulska published I Came Back, and throughout the 1950s there was a stream of biographies of victims including Danielle Casanova (1953), Edith Stein (1955), as well as other memoirs and more scholarly works.

There were other movies with Holocaust themes, including Orson Welles’s 1946 The Stranger, which featured footage from concentration camps

Fred Zinnemann’s 1947 The Searcher describes Auschwitz survivors looking for each other, while Kirk Douglas starred in 1953’s The Juggler, as a Holocaust survivor.

The Nuremberg trials also received very widespread media coverage.

Publications accelerated during the 1960s as people recovered from the trauma, acknowledged that their survivor’s guilt was unfounded, and decided to tell their stories, or wrote about their parent’s experiences.

The point is, extreme trauma such as the Holocaust can take years or decades to come to terms with before survivors are able to tell their stories. But, the existence of these and other books and movies, in addition to news media coverage, indicate widespread knowledge in the late 1940s and 1950s.

(Edited to fix horrendous misspelling of Zinnemann.)