Look, my point is that there is a lot of oppositional leaders in Russia. There are TV channels, radio stations news papers and a lot of online publications that blast Putin for everything under the sun. Navalny is, by far, not the only one who “dares to speak the truth”. And I salute that.
The court had sentenced him to 5 years suspended sentence for a very real case with some very hard evidence against him. Why do you think that it’s an “obscure reason”? Are you a lawyer?
Navalny doesn’t have nearly enough following to become a serious candidate, so Putin’s regime doesn’t need to do anything. In fact Nemtsov, as crooked as he was, pointed out that Navalny doesn’t have a chance in his phone conversation with (I think) Kasparov.