They don't actually explain anything. You don't really understand anything that really happened until much later, because of this >>12548255
, and even then some stuff is missing from the film.
Nasu likes to ramble about life and fatality and stuff. If you like that, you read/play his works. If you don't, you don't. The stories are not made more complicated by this, just the mechanics that make the world go become more complex. You can easily get the entirety of the story just by reading the obvious parts. Of course, if you are reading something in a style you don't like, when there are already a zillion examples that it's that style that is going to predominant in the story, one has to wonder why the fuck you're reading it in the first place.
Third, everyone forgets this is a NOVEL ADAPTATION. In the novel, you didn't need to wait months to read the following part and eventually get everything to fall in place. This shit isn't standalone, and while the adaptation is well made, it's imposible to convert an episodic novel into seven wholly standalone segments that can work well by themselves.