Lenin was acutely conscious of the dangers of parliamentary cretinism: socialists treating parliament as the primary arena of struggle and subordinating everything to its priorities. This would bend socialists’ politics towards compromise with capitalism and also their practical orientation to parliamentary manoeuvring. He was equally alert to the problem of voter fetishism: voters mistakenly thinking the vote is an exercise of power, when in fact power in a capitalist society is collective, social and located largely outside the parliamentary realm. Elections had a place, but they were no substitute for mass working-class action in the workplaces, streets and squares. Ultimately power must be wrested from the capitalist class in revolution. Source
And in becoming so focused on identifying pitfalls against combating capitalism, some of which were completely hypothetical and theoretical, Lenin became blind to the consequences of the attained power consequently corrupting purported socialists.
The USSR was a failure of revolutionists to correctly wield the power they had attained, and instead of controlling it, it controlled them. Lenin was so focused on wresting power from capitalists that he did not consider safeguards on that power.
He was alive to see the revolution succeed and the Bolsheviks take power, and remained healthy and in power for a few years. He didn't set up a strong, foundational government.