These are just assumptions. Navalny is a rich right wing liberal, most of his base is in Moscow and St. Petersborg, getting 30% in the best poll in his base city is not very impressive. I also don't know about him appearing out of nowhere, I am pretty sure I have heard the phony hype around him for years now.
Given the fact the amount of people turning up to vote isn't somehow too low in Russia there is no need to suspect what you do, not to mention old people (largely Putin voters) are notoriously stoked about voting. My own grandma votes every time in every election (ironically it is almost always the communist party she votes for).