In the 1880s and 1890s there were several major scandals that rocked the world of professional rowing. By 1900, the sport had fallen in such disrepute, it became extinct due to all of the chicanery, race fixing and dastardly cheating that went on. In 1919, that sorry series of events was within living memory of the powers to be in big league baseball. They did not want to see their sport suffer the same fate, so they came down like a ton of bricks on the Black Sox.
http://www.rowinghistory.net/professionals.htm