From what I've read in the past, my understanding is that:

• There has been pretty strong statistical evidence that there has been a substantial level of vote-rigging, where the reported vote numbers are extraordinarily unlikely to actually come up by chance. ("When Dmitry Kobak and Sergey Shpilkin, two researchers, analysed the results, they found that an unusually high number of turnout and vote-share results were multiples of five (eg, 50%, 55%, 60%), a tell-tale sign of manipulation. According to Messrs Kobak and Shpilkin, there were at least 1,310 polling stations (out of 96,325) with results that were suspiciously tidy, with rounder numbers than you would expect to see by chance. Although it is difficult to pin down precisely how many votes were affected, the researchers estimate that such fraudulent results may have boosted United Russia’s vote share by nearly 20 percentage points. Other, less obvious forms of cheating may have taken place too. ")

• However, aside from this, I've also seen material stating that Putin would probably still win a majority vote against the other candidates. That is, it's not false reporting of voting numbers that's driving all this.

• A broader issue is that the electoral environment isn't free and fair. Navalny is in jail, and there were attempts to assassinate him, and people associated with him have been jailed. Nemtsov was assassinated. Independent media is subject to restrictions. It's hard for serious opposition candidates to make real runs.

To give a more-extreme example, North Korea does, in fact, have elections.

Now, there are some pretty big caveats to these elections.

• The approved candidate is the only option; you simply announce whether you approve or disapprove. Hypothetically, if most people disapproved, there would be another vote and some other candidates would be added.

• The ballot is not a secret one; officials can see how a voter votes, as there are two separate boxes for votes against and votes for.

• The ruling party oversees the candidate selection.

• There's no independent media.

• And there's of a history of unpleasant things happening to people who politically clash with the government.

https://www.nbcnews.com/news/world/kim-jong-un-wins-100-votes-north-korea-election-n49011

North Korea's state media confirmed on Monday what was surely never in doubt — a 100 percent, no-abstention victory for leader Kim Jong Un in the country's stage-managed parliamentary election.

But in theory, there's nobody with a gun making someone vote at the ballot box. Hypothetically, you could vote in opposition.

Now, I could easily believe that someone, in fact, did vote in opposition somewhere in the country and it wasn't reported, but point is, it's not false reporting of vote numbers that is the dominant factor in structuring things such that the people in power are going to stay in power in North Korea.

Russia isn't as extreme a case, but same point: it's not simply that elections work the way they do in random country that has an open political environment and then someone lies about the numbers. There are a number of processes going on.

Why not both?

They have been stuffing ballot boxes for decades.

Maybe other candidates go for a window altitude sky dive

They don't need to lie. Votes are anonymous. A lot of people work for the government companies, like school teachers, doctors, etc. They get rounded up, loaded into buses and given pre-filled ballots. Then the bus travels around polling stations, all these people are forced to go and drop pre-filled ballots. They do that all day long or else. And then you have Putin win with 146% of votes.