A matter of timing
If we assume that Lvov soon shows that he is willing to make peace first with some secret negotiations leading to a late April armistice and a May peace treaty then there is no sealed train. However once peace is formally concluded there is the question of whether Lenin, no longer a belligerent national, is permitted to make his way home. My best guess is yes but not right away as the Third Military Council might fear he might undo the new peace. So in late June or early July a very ordinary train arrives at Petrograd with Lenin just another passenger.
So the "April Theses" are delayed and thus not presented to the All-Russia Conference of Soviets of Workers' and Soldiers' Deputies. It should be noted that before the April Theses the consensus amongst the Bolsheviks was to cooperate with the provisional government. When Lenin does arrive ITTL he will probably make similar "June Theses" but the timing is off. Russia is demobilizing with workers returning to peacetime occupations. This is why I believe that if Lenin does attempt a power grab it will be in 1918 not 1917.
Why are people getting the impression that Russia withdrawing from the war early somehow prevents Lenin from getting home?
If we assume that Lvov soon shows that he is willing to make peace first with some secret negotiations leading to a late April armistice and a May peace treaty then there is no sealed train. However once peace is formally concluded there is the question of whether Lenin, no longer a belligerent national, is permitted to make his way home. My best guess is yes but not right away as the Third Military Council might fear he might undo the new peace. So in late June or early July a very ordinary train arrives at Petrograd with Lenin just another passenger.
So the "April Theses" are delayed and thus not presented to the All-Russia Conference of Soviets of Workers' and Soldiers' Deputies. It should be noted that before the April Theses the consensus amongst the Bolsheviks was to cooperate with the provisional government. When Lenin does arrive ITTL he will probably make similar "June Theses" but the timing is off. Russia is demobilizing with workers returning to peacetime occupations. This is why I believe that if Lenin does attempt a power grab it will be in 1918 not 1917.