Hard to disentangle effects from other stuff that was going on. Prohibition was repealed in 1933, in the depths of the Depression. It was also the year before FDR signed a comprehensive crime-fighting bill that allowed FBI agents to carry guns and make arrests.
By pure numbers, crime did hit a 20th-century high in 1933, right after prohibition was repealed, and they didn't pass those numbers until the 1970s-early 1990s (and only just barely then). But this was also the economic nadir of the century. And the mechanism for the decline in organized crime was that many crime bosses were killed or imprisoned, so it could've been the crime bill. So yes, it is what happened at the end of prohibition, but it's hard to draw firm conclusions between the two.
