Because if a fanfic is so good that it has its own fanfic, sooner or later someone has to do this.
The Authors we see during the No Fourth Wall moments are actually interdimensional beings.They appear out of nowhere and warp reality for their own pleasure. Obviously, Legend Maker is a more benign Lovecraftian entity playing games with mankind. And, following on that theory...
Robert is a fledgling Author.There actually is plenty of evidence. We know that the Authors warp reality and break the Fourth Wall, and that they have a share of genre saviness. While most characters are punished for breaking it, Robert does so almost constantly with very few problems, to the point where there is No Fourth Wall for him. As for the reality warping, he does it on a small scale all the time. Pulling those pamphlets from nowhere, as well as other esoteric items like The Junior Hero's Guide to Plot Cycles in Wings of the Eagles, and the ACME items from Adeste Fidelis. Even getting the Gauntlet was him unconsciously exerting his powers. He manipulated Pangloss and the laws of chance by using the Theory of Narrative Causality. This is, incidentally, also why Noel doesn't like him. Being a creation of Legend Maker and the first introduced OC, he knows about Robert's Author abilities even if Robert himself does not, and fears that he will destroy/rule the universe upon finding out. Basically, Robert is the American response to Haruhi Suzumiya.
If we have a crazy theory about Robert, we need to have a crazy theory about Noel. It keeps the universe in balance. Therefore... The entire series is a Gambit Roulette designed by Maxwell Collins to turn Noel into his perfect sucessor.Maxwell knew beforehand about the trucks, as his scientists had been working with the experimental neurotoxin carried by one of them and accidentally discovered a sort of proto-Shimmer. It died without a host, but he saw the potential. He also knew that the age of metahumans was coming up, and decided that his sucessor would need to have a power. Things fell into place when he discovered Noel's plans to run away, and knew where they would bring him. So he engineered the truck crash and has observed and subtly guided Noel ever since. There were a few things he didn't plan, like the Lord of the Night, but he still managed to benefit from them, e.g. having the Lord destroyed kept him safe. Think about it. Living with the Titans and fighting constantly has made Noel cunning, cynical, calm in the heat of battle, and occasionally ruthless... In other words, the exact qualties needed to replace his father. It's also given him connections, enough so that he can take things even farther than Maxwell did once he is finally brought back to his side.