I don't know if you're aware, but Putin is genuinely popular in Russia and will likely win any election, even if they are "free and fair" under Western standards (which they will never be, because it is in Western interests to portray Russian elections as not free or fair). When you see statements like "the elections are rigged", keep in mind that the Western media (with a few exceptionsa few exceptions) is trying to push the idea that Putin should not have won.
You can see indications of this in your original quote. 763 votes for Kharitonov, 73 for Putin makes it sound like the sky is falling for Putin, which is what the Western media is shooting for. But when you take into consideration that there were roughly 80 million votes cast, a difference of 700 votes will have literally no impact on the election results. It's not dissimilar from how Trump perpetually harps on a few hundred disputed ballots to "prove" that he should have been the winner in the 2020 US Presidential election.
Once you accept the idea that Putin is genuinely popular in Russia, then the answer is obvious enough: if you support Putin, why wouldn't you vote?