To me, it seems there are two different gameplay styles/"metas" in League of Legends. I've noticed this being mentioned in other threads and some in this thread appear to be dancing around this issue. One is what we all know: the pro meta, in which there are unwritten rules which everyone abides by. Some players end up not quite grasping these concepts and forming what ends up being a rather foul mutation of the pro meta. This is how most low ELO games are played, and instead of playing intelligently, the players throw themselves at each other until someone dies. As a result, games become a one sided stomp as one player gets grossly fed and another feeds without any knowledge of how to stop it. At this level, characters such as Trydamere, Xin, and Master Yi get popular because no one in the match the summoners are playing can figure out how to stop one after first blood. Usually, this requires full team cooperation and a change in tactics, which are sometimes foreign concepts to these low level players. Now, throw in someone who has evolved past this meta, by learning the game better, or even someone being placed in these matches unfairly (a result of bad luck, perhaps), and you have ELO hell. This person will attempt to play by the pro meta, and because the rest of his team doesn't know how to do so (thus countering low ELO stratagies), the mid-high level player will be hopelessly crushed. A common way of raising your ELO past such a point is to play by the low ELO meta, and use your skills to always get fed with a pubstomper until the game quality increases, although if a player isn't used to these champs, they will be unsuccessful. It doesn't help that ragers, who often have this berserker mentality, tend to hang around this ELO and scream at the team members that don't get ridiculously fed. As mentioned, the system used by multi-queued users brings these people into the range of the pro meta, effectively screwing the people on their team.
I'd like to use a recent game I had, and unfortunately, I don't have anything more than an note in my game history. A team of 4 players was matched with me as the 5th. Our Fiora got fairly fed (and cocky) fairly early, and began making bad decisions. Although she did the most damage, and got the most kills, she also died more than anyone in the game. In one instance, she took out a few members of their team, and instead of teleporting to base when low on HP, decided to try to get more kills. When the rest of the enemy team arrived, she was CC'd to death. Similar things happened quite often when she tried to fight the enemy in their territory alone. Combine this with the rest of her clueless team, the other team got fairly fed, too. Now, I was playing Kog bot lane with a Galio that gave up a couple kills, and I quickly became underfarmed compared to everyone else simply because I decided to attempt to farm rather than risk feeding. Caitlyn became a threat, and I was then unable to do that, even. My teammates engaged rage mode, and because I played by a different style than my team, I had a hard time doing much of anything in game. The other team, however, coordinated (and played by the pro meta) enough to shut down our Fiora as she blindly rushed into a fight. Other examples of poor decision include an attempt at Baron when all 3 lanes were pushed past our side of the river, and the enemy had map control. Sure enough, they showed up and quickly disposed of us. You can figure out who they blamed for this.
Why is it harder to win a 1000 ELO game than a 1600? It's simply this difference in the overall team level. Low ELOs fluctuate too much between games because of the poor tactics, and people who don't use low ELO tactics are punished. This is partly why the matchmaking shouldn't punish win streaks- it shows that the player is consistently better than their current level.
Please note that the usage of "pro meta" and "low ELO meta" might not be 100% accurate, and are just terms I decided to use to describe the situation. Also, the complete idea is not mine alone, but created by many on this forum.