Q:

Why Vladimir Ilyich Lenin is so popular in Russian?

Recently I have seen a documentary film from "Star Media" (this is Russian film) called "The first world war". Up to this moment, I thought that the February Revolution had happened, because there was a huge economic problem and people were living in very poor conditions. Now I understand that the world war continued and this problem is obvious (but I didn't think about it before). Next, according to the film (and I believe it's true), the Bolsheviks signed a treaty of peace with very bad conditions for the Russian Empire (the Russian Empire had to pay reparations and lost some territories). 
So now I'm confused, how did the Bolshevik's leader become so popular in Russia and have a lotof monuments?

A:

This contains several questions. First, why was Lenin (more exactly, his party) popular in 1918-1922. The short answer is "because they distributed landowners land among peasants" (Only to seize it back after 15 years of dictatorship).
Second, why was he popular after his death, and until now.
Because his successors who established a dictatorship in the country with total control and huge propaganda apparatus created a cult of Lenin. They, the
ruling party,  not the people, erected all those monuments. For several generations the population was intensively brainwashed (and the part of it which resisted brainwashing was physically exterminated). These rulers maintained the cult of Lenin which exists (to a smaller extent) even now.
In the independent Ukraine people destroyed all monuments to Lenin in a short period since 2014.