It was the October revolution, rather than the earlier March revolution that really brought about change and the institution of the Soviet Republic and it was the Bolsheviks who took power at that point. That is why the October revolution is so named.
It was a planned revolution, unlike the March one which perhaps we might call a revolt. Lenin's ideology was well known earlier than that year, but it had less direct influence in March than in October. He had been in Switzerland until April but on his return called for the overthrow of the Provisional Government, the transfer of "all power to the Soviets."
He also suggested the expropriation of factories by workers, and that the peasants should take over the land belonging to the church, the nobility, and the gentry. Lenin's dynamic presence won other Bolshevik leaders' support and the October revolution proceeded.