I have not seen the movie, read the graphic novel/source material, or read any reviews other than this forum, nor have I rewatched any episodes. Here is my speculation about Mr. Wilford:
He is from an alternate universe that operates in four dimensions. As part of his Masters thesis, he researched probable causes of apoplectic demise. For his Doctorate, he created microverses of the earth, which are contained in shadow boxes like ant colonies, or globes like snowglobes, and created different crisis for each one to see how the humans could survive. There was one for the The Cretaceous-Tertiary extinction event, one for the wheat blight, one for the dust bowl, one for the Spanish flu and a follow up of a contagious virus in 2020, and the one shown on the show, global warming.
Since they are microverses, a minute in his real time is equal to a year in each microverse, and he is able to jump in and out of the shadow boxes by teleporting to specific leylines. That's why Ruth found a strange man without a car or luggage showing up at her B&B, why they need ten miles of train, and why it was a concern in episode one when they were behind where they needed to be. As long as the train is moving, it doesn't seem like it would matter where it was on the track, but if it doesn't cross a leyline at a certain time, then Mr. Wilford is unable to land on the train as opposed to the frozen ground. The need to cross the leylines also explains the map someone posted that shows some weird sharp turns that do not make any sense to those of us in this reality.
The theory gets stupider...
As part of his research, he must allow the subjects to act of their own free-will without his involvement. After realizing the human race is too stupid to not destroy the train during their efforts to advance their personal needs, and just cannot get along, he is left with no other option then to arrive, all Gandalf-the-White-like with a staff that shines a bright light throughout the train, all Godlike:
He then bellows, which reverberates throughout all 1001 cars of the train:
"If you do NOT stop fighting this instant, I will pull this car train over and put all of you out on the side of the road track!!! Anyone who does not want to live under my rules is free to leave. Raise your hand and a Brakeman will lead you to the last car and you will be disconnected at the first side rail we cross!"
He then returns to his reality where he grumbles about mankind, bitches about not using mice or ants like normal people, and downs half a bottle of Jack Daniels.
This petty bitching was brought to you by chronic insomnia but not drugs (because I don't have any) and not alcohol (because Mr. Wilford drank it all). I'm hoping the last episodes drive the show home, but right now, it doesn't look like it will happen.