Organized crime led only indirectly to the end of Prohibition. The rise of organized crime helped to reduce the enthusiasm that people felt for Prohibition. This meant that it had less political support and, eventually, that it could be done away with.
When Prohibition went into effect, legitimate companies could no longer supply alcohol to people who wanted it. However, Prohibition did not prevent people from wanting alcohol. Therefore, there came to be a huge demand for illegal alcohol. Organized crime, which had not previously been a very big “business” expanded greatly to fill this demand. The most famous example of this was the rise of Al Capone and his gang in the Chicago area. They made tremendous amounts of money providing illegal liquor to people who wanted it.
As the 1920s wore on, it became clear to many people that Prohibition was helping cause the rise in organized crime. Many people who might have been in favor of Prohibition at one point came to feel that its negative effects (including the rise of organized crime) were too severe and that they outweighed any benefits that were being felt. Their loss of faith in Prohibition helped to reduce its political appeal and helped to make repeal possible.