I'm always wary of talking about the lineage of 'ideas' when it comes to examining specific policies or state structures. There is no direct line, for example, between Marx and the early USSR. That might sound crazy but Marx left no blueprint for a socialist society and the state constructed by the Bolsheviks emerged strictly on an ad hoc basis. Even the plans laid out in Lenin's last great theoretical burst - in 1917 when he 'rediscovered' Marx and reinvented Marxism* - lasted less than six months when confronted with the reality of governing and civil war.

On taking power Bolshevik policies were dictated by the various economic, political and military crises that faced them, not some pre-determined ideological programme. (While still being constrained by broad political assumptions, eg the superiority of centralisation and non-market solutions.) Their actions had to be justified with reference to Marx but theory was very much subservient to action. Karl Radek once joked that Lenin was 'a true Marxist: he makes his decisions on the basis of facts, and only then builds his theories explaining those decisions of his'.

This continued throughout the 1920s and onwards. The Bolsheviks produced surprisingly few notable theorists during these decades and there's very little that's novel in the likes of Socialism in One Country. Marxism, outside of economics, was not a major dividing point in the struggles of the 1920s and the efforts of the 1930s looked back to the 'heroic period' of the Civil War than to the Manifesto.

Which is perhaps digressing a bit. In practical terms the Lenin period and NEP left the USSR with an intact state and economy. It provided a firm launch pad for the subsequent Stalinist take-off. Which given the state of the country in 1918 was no small feat. But the policies of the late Lenin period were to be reversed (Lenin was likely sincere in his embracing of the NEP) and the state apparatus was largely rebuilt during the Stalin revolution. This was essentially a re-founding of the USSR.

So plenty of Stalin's policies broke with those of the past, enough that we can talk of 'Stalinism' as a distinct period. Does that disqualify Stalin from being a 'spiritual successor' of Lenin or sharing his core ideas? That's something people are still arguing over.

*And it's worth stressing that the Lenin of 1917 was in many ways proposing radically different approaches to the Lenin of the Second International.