One of the most important parts of the movie "The Circus" was the impact of the Karkat's Ultras. One of the major subplots of the game was how the subsequent heroes would deal with their bizarre forefathers. They did not follow through on this threat, but this was only because they were too far gone to change their minds. There are many episodes that can be inferred from this; but the biggest of all is in the act of what they do next.
After the defeat of the heroes, Aradia agrees to the trashing of the Art and the players are left without a past. Afterward, they go to the past to fix the mistake of their forefathers. They discover that they are unable to reach the future to destroy the Grief Seeds due to the presence of the Ultras, but this makes sense. They had destroyed their own future by sacrificing themselves to save the past! In order to redeem themselves, they have to make things right.
We learn a lot more about the Karkat's Ultras after this point, and one of the major points in this aspect is the influence of time travel. The future that they destroy is simply a possible version of their future, so in order to find the right future, they must find the true version of the future first. What exactly did they do wrong? This is one of the main threads of the movie.
While they try to figure out the big reveal, we see the beginning of the Cenabites. Their presence is later shown to be connected to the subsequent destruction of the line. This only establishes that our heroes are the catalyst for the end of the line, but it also makes the entire scenario somewhat of a mystery.
At the end of the episode, Karkat takes the camera back to find the final moments of the movie: the appearance of the Karkat's Ultras and the death of their selves. This event only seems like a trick, but in fact, it is an important scene in the story and not a moment of 'art.' We never really knew if the Superflat was going to get another shot at revealing what really happened, so we never got to know if the Cenabites was actually a failure or a success.
Not only that, but at the end of the movie, we learn that the entire event was simply part of the Game. It was all a test of the heroes' abilities to learn from past mistakes and so long as they successfully made the other mistakes, then they would return and do it all over again.
It was a brief moment of redemption for Karkat and his friends, but it was also the end of the game. It was the ending of an experiment, a way for the game to show the consequences of their actions, but this was the only time where it showed any sort of good outcome.
Artists often avoid this type of analysis, mainly because they want to keep the focus on the art. In the end, what you want to do is appreciate the art and the game, not the idea of criticism.