The ukulele slowly declined in popularity through late 1920's and 1930's, with Wall Street collapse being one of the reasons.
It saw a temporary revival in the second half of 1940's thanks to actor and singer George Formby and US servicemen bringing the instrument home with them from Hawaii.
Ukulele remained a relatively popular instrument during 1950's becoming a mass produced prime instrument for kids.
From 1960's popular music becomes to be dominated by traditional guitar bands pushing ukulele out of spotlight.
It would take nearly 4 decades for the instrument's revival. Ukulele, thanks mostly to internet is now regaining its former position as one of the most popular instruments.