Russia has a long history of having criminal gangster leaders. Joseph Stalin for instance... former bankrobber, kidnapper, gangster who went on to mass murder... So Putin is really just taking over where Stalin left off.
To eradicate accused "enemies of the working class", Stalin instituted the Great Purge, in which over a million were imprisoned and at least 700,000 executed between 1934 and 1939. By 1937, he had absolute control over the party and government.