Lenin intended to keep the NEP temporarily yet it lasted 7 years until Stalin abandoned it. It feels like Lenin was more moderate and willing to accommodate changes to maintain stability. It seems like the NEP succeeded far better than expected. Lenin did view the NEP as state capitalism but then why did it last so long? Did he ever reconcile that this state capitalism could be useful for a long-term ease into socialism?
The NEP lasted so long, because the prefered alternative was very hard to implement. Many beliefed collectivisation could not be done, or if it could it would be to costly. It took a guy with the power and will of Stalin to implement collectivisation.
The NEP was successful in brining food and stability, but it did not allow the communist to implement their agenda of rapid industrialisation.
There were some in the leadership that wanted to keep the NEP, but non of them fully admited to the very long term necessity of private property. It was unlickly that Russia would go the way that china went.
Maybe if people like Alexei Rykov, Nikolai Bukharin and Grigori Sokolnikov had achived a position of power, they might of turned to establishing more permanent policy along the lines of a NEP when challeneged with reforming the system.
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Check out this video by the auther about your question: https://www.youtube.com/watch?v=xtKqn_Ts-m8