Why were party leaders shocked by krushchev’s rejection of stalin?

In February, 1956, Soviet leader Nikita Khrushchev made a keynote address to international communist leaders at the Twentieth Congress of the Communist Party of the Soviet Union. He used his speech to make unexpected and unprecedented condemnations of the policies and excesses of his predecessor, Joseph Stalin, setting off a chain of reaction that led to calls for reform in Eastern Europe and a new policy in the Soviet Union for dealing with the West. If this is not the answer you are looking for please dm me or comment :)

The answer is ethnic groups.