Soul Train went into reruns because they ran out of new R&B/Soul they could dance to.You can only play so much Beyoncé or hip-hop per show. Alternatively they couldn't book anymore guests after awhile. Hell they couldn't get people to show up for the award show. And them giving Ashanti a lifetime achievement award sealed it's fate.
It's cancellation was pettyThe REAL reason it was cancelled was because people didn't want it surpassing American Bandstand.