The use of effective propaganda, 'Bread, Peace and Land' was simple, concise, easily repeated even among poorly-educated peasants: a brilliant political slogan! 'All power to the Soviets' - again, simple and catchy, even if Lenin did not intend to enact it! Followed by effective propaganda is good leadership skills. Lenin was an "orator of enormous impact and power, breaking down complicated systems into the simplest and most generally accessible forms" and hammering them home with his audience.
The help from others also helped Lenin rise to power. Lenin was helped by the Germans. They helped Lenin travel in a sealed train through Germany on his way back to Russia in 1917, in the belief that revolutionary agitation could only weaken the Russian war effort in World War 1 to their advantage. What also helped Lenin enormously, was the Provisional Government's failures. Kerensky's made many mistakes. First in continuing the war and refusing to take a stand on the 'land issue', and then in arming the Bolsheviks and allowing them to be seen as the heroes during the Kornilov affair. As the Provisional Government became more unpopular, the Bolsheviks increased their support over 1917.
There were many reasons why Lenin was able to rise to power but the the April Theses, effective propaganda, attractive ideology, good leadership skills, and the help of others were the biggest and most important reasons why Lenin was able to become the leader