The Global Influence of the Russian Revolution and the USSR

The Bolsheviks encouraged colonial peoples to follow their experiment. Many non-Russians from outside the USSR participated in the Conference of the Peoples of the East ($1920$) and the Bolshevik-founded Comintern (an international union of pro-Bolshevik socialist parties). Some received education in the USSR’s Communist University of the Workers of the East. By the time of the outbreak of the Second World War, the USSR had given socialism a global face and world stature.

What issue concerning the style of government in the USSR during the $1950$s led to a decline in its international reputation as a socialist country?