Causes of Reincarnation

If Buddha didn't believe in soul why did he believe in Re-incarnation, after life etc which could be because of soul ? What causes one to be born again, is that the desire, if it's the desire, Buddh's belief is the same as told by Krishna(who is supposed to be the previous incarnation of Buddha) who said "what you think at think about at the time of dying, you will be born likewise" Is the desire main cause of "Re incarnation" ?