I can’t really speak to Kruschev’s reforms.
With Deng, the key element was addressing underutilized production capacity. There’s a problem you get in planned economies where regional and local planners have an incentive to always meet their production quota. Which leads to, requesting more raw materials than they actually need and promising less than what the factories or factory are capable of. Hence the Soviet factories that would have raw materials and/or finished goods just piled up collecting dust.
The Deng reforms changed this to be, the regional and local directors had their quotas they had to hit for the planned economy’s needs. However, after that they were free to use their surplus productive capacity to produce goods to sell on the market. And, as others pointed out, this was coupled with opening up the Chinese economy to export to capitalist countries. This both resolved the underutilized production problem while bringing in trade dollars, all while retaining a most state-owned economy; as these corporations emerged out of the state production infrastructure, the state was a majority or major owner from the start.