what's wrong with watching a let's play and then voting for the game? You still saw the game. Especially when it comes to story driven games, I don't see why this is a problem. I voted for several games through secondhand experience, either by being on stream with a friend or watching a video later. I don't think these sorts of votes are the ones people are questioning, at least in my opinion, those are still valid.
Viewing post in Rating irregularities
yes they are valid but the fans are not real, they were told to do something and left. This is common in Kickstarter, steam and social media post. The people who voted will not return to play the game, they were told to do something by a person and then they had nothing else to do for that game. Some might still be following but lots of the fans are just vote and leave kind of people.