I am certain that Shoigu, or Mishustin, or Rogozhin, or the same Medvedev again, could all replace Putin just fine should a need arise. As I wrote, that would be a small change anyway, and not necessarily for the good.
Navalny, on the other hand, never had a chance, unless the vote for Russian president was done among the US voting populace. In that case, he would no doubt win a landslide victory. In Russia outside of the Moscow intellectual spheres, he's simply unknown — it's not that the people in Vorkuta hate him, they don't know who he is (was) to begin with.
In the USSR media of 1980s, there was a lot of talk of Angela Davis, she was the undoubtful "opposition leader" in the USA, as presented by Soviet media. Navalny is in the same position.
