While it’s impossible to give an absolute answer to that problem, we must remember that people change their ideas based on their material conditions. Stalin mentions how this exact problem was dealt with during the 1917 revolution:

To put in the forefront precisely those forms of struggle and organization which are best suited to the conditions prevailing during the flow or ebb of the movement at a given moment, and which therefore can facilitate and ensure the bringing of the masses to the revolutionary positions, the bringing of the millions to the revolutionary front, and their disposition at the revolutionary front.

The point here is not that the vanguard should realise the impossibility of preserving the old regime and the inevitability of its overthrow. The point is that the masses, the million should understand this inevitability and display their readiness to support the vanguard. But the masses can understand this only from their own experience. The task is to enable the vast masses to realise from their own experience the inevitability of the overthrow of the old regime, to promote such methods of struggle and forms of organisations as will make it easer fro the masses to realise from experience the correctness of the revolutionary slogans.

The vanguard would have become detached from the working class, and the working class would have lost contact with the masses, if the Party had not decided as the time to participate in the Duma, if it had not decided to concentrate its forces on work in the Duma and to develop a struggle on the basis of this work, in order to make it easier for the masses to realise from their own experience the futility of the Duma, the falsity of the promises of the Cadets, the impossibility of compromise with tsarism, and the inevitability of an alliance between the peasantry and the working class. Had the masses not gained their experience during the period of the Duma, the exposure of the Cadets and the hegemony of the proletariat would have been impossible.

The Party would have become detached from the working class, and the working class would have lost its influence among the broad masses of the peasants and soldiers, if the proletariat had followed the “Left” Communists, who called for an uprising in April 1917, when the Mensheviks and Socialist-Revolutionaries had not yet exposed themselves as advocates of war and imperialism, when the masses had not yet realized from their own experience the falsity of speeches of the Mensheviks and Socialist-Revolutionaries about peace, land and freedom. Had the masses not gained this experience during the Kerensky period, the Mensheviks and Socialist-Revolutionaries would not have been isolated and the dictatorship of the proletariat would have been impossible. Therefore, the tactics of “patiently explaining” the mistakes of the petty-bourgeois parties and of open struggle in the Soviets were the only correct tactics.