I read this in the source cited in this answer
Initially the Soviet assistance in China’s nuclear programme was limited to the civil nuclear energy field. However, Moscow’s attitude shifted in 1957 when Khrushchev needed the support from the CCP leaders in dealing with the political struggle within his own party. In return, Moscow signed a comprehensive weapon technology transfer agreement with Beijing in October 1957 that included provision for additional Soviet nuclear assistance as well as the furnishing of some surface-to-surface, surface-to-air, and anti-ship missiles.
Question is: what could posibly the CCP do for Khrushchev in his interal power struggles?