If you knew why, it would defeat the purpose since you would know the consequences to the game. As far as factions go, you get the basics from the intro and the tips of each term, but the decisions you make are not meant to be based on "I like x faction" but rather what you think of the given circumstance without any other context - that is your role in the world to begin with - arbitrate / judge etc (or do what you like because why not!)
"Why" as in why should I care about these choices? I don't want to know the exact consequences of these actions yet obviously, but the game did nothing to establish anything and just threw me into what a good story would do at the end of a game.
I don't think my role in the world is to make a decision without knowing the context at all actually, seeing as how most of these games are about giving you that exact context so you can actually make interesting decisions.
The choices basically were: which one of these two factions, who we just wrote 3 lines about, do you want to piss off the least? Well I know one of them is an elite small force and the other is join us or die, that's it. The choices are totally random because how can I form an opinion on it without any context as to why this decision MIGHT get me here or there or "i cant piss these people off about this even though i dont like them because i need them to help me build this thing over here".
These are the kinds of decisions you make at an end or midpoint of a game, after you know why these decisions matter.
To me they will probably only make sense on a second playthrough.
It's not a huge deal, just a general problem I see with many fantasy games.