Unfortunately propaganda works. And the Russians have been working at it for a long time. To be fair, so has the West. There are absolutely Russians out there who believe in conspiracy theories we've spread.
The problem of course is that propaganda like this is self serving and generally impedes the progress of civil society. We can't recommend a change in our government without getting called a dirty commie and lumped in with these guys. Russians can't do it either, not without being called a Western traitor and arrested. And yes I realize those are two different outcomes, the point is the problem is just as hard to get around.