Living under a dictatorship tends to weed out the heroes over time because they will want to change things, stick their head up out of the grass and have it chopped off. This tends to discourage the rest, understandably.
Russia doesn't have a whole lot of powerful people besides Putin left, he's either killed, jailed or neutered them. This is a major cause for concern right now, but it is also exactly why it is that way: dictators do not like viable competition.
Don't bring a democratic countries' viewpoint into a discussion about what the people living in a dictatorship can or can not do. It is possible, but only if there a sea change in support of the government, and with the media under total control unfortunately Putin is still ridiculously popular in Russia. And this may not change sufficiently, taking into account that he will blame any and all hardships on the West.
I believe this is a good definition of cowardice. People indeed do it all the time.