Answer
The Bolsheviks turned on Makhno because they feared his growing power and popularity. The Makhnovists had defeated the White Army, which was the main enemy of the Bolsheviks, and they were seen as a threat to the Bolsheviks' power. The Bolsheviks also did not agree with the Makhnovists' anarchist principles, which the Bolsheviks saw as a threat to their own authority.