He has a frighteningly efficient secret police following. They quickly and quietly "dispose" or put anyone who opposes him out of touch. There's a large number of former employees and opponents who have "disappeared" - apparently related to opposing him...but hard to confirm.

"Vladimir Putin likes to associate today’s Russian Federation with the old Russian empire, and in one sense he is right. The Russian empire was the most repressive state of its era, with the most refined state police: the Okhrana. Russian revolutionaries, the men and women who would establish the Soviet state, were educated by its methods. It did not simply hunt them down; it ensnared them, often without their knowledge, in a complicated dance of incriminating their comrades. It specialized in provocations. It knew how to make its enemies do the work for it."

Read more, here;

[theatlantic.com]