Odd to frame this as a story about the 1920s when one of the quartet, Wittgenstein, spent the decade in philosophical exile. He finished the Tractatus in 1919 and didn't return to Cambridge until 1929.
He never stopped thinking about philosophical problems, and when he returned to academia his views had changed radically.
True, but the 1920s were easily his least active, philosophically. He did most of the work for the Tractatus in the 1910s; most of the work for the Investigations in the 1930s.
He published Some Remarks on Logical Form in 1929. It's been 10 years since I was reading Wittgenstein, but my recollection is that work was still Tractarian. The blue and brown books came in the 30s.