Khrushchev had rivals within the Soviet government, and the de-Stalinization movement was a way for Khrushchev to gain the good will of the Soviet people.
After Stalin's death in 1953, the USSR initially was run by a trio of other leaders. When Khrushchev was named First Secretary of the Communist Party later in 1953, he needed to distance himself somewhat from others and show that he was not going to be the same kind of leader that Stalin had been.