Okay, the title is paraphrased from an equally paraphrased quote about states.*
The shifting alliances in a megadungeon can be looked at in geopolitical terms to get a different perspective on how and why they act in a particular manner. Each group or individual power is an actor. How they interact with each other is tied to their interests.
The idea here is that it's not "Who are the goblins friends with?" and "Do the ghouls have any friends?"
It's "what are the goblins' interests?" and "what are the ghouls' interests?"
Not likes and dislikes, but wants, needs, desires, goals, etc.
A group of PCs is an actor in this arena, too. What is the group's interests? Who do they need to ally with, who do they need to fight, and who do they need to ignore to further those interests?
It's also a reminder that negotiations with folks outside your group of friends is not a personal thing. It's done between people (or things, or things which as also people) but it's not about friendship. It's not about likes and dislikes, although they may affect who you'll actually be able to strike a deal with. Business is business, basically - if it's not good business to continue an alliance, or if your interests lie in ending it, you end it. Of course, this goes both ways. Your ally now can be an enemy later when your interests conflict, or your enemy now can be an ally later when your interests match. If you take it personally, you're confusing a shift in relationships with personal betrayal. Revenge is a personal feeling, it's not really a basis for pursuit of your goals.
This also can help you see more clearly where opportunity lies. If the interest of the goblins runs against the interest of the ghouls, they will come into conflict, even if they seem to get along. You can play on that conflict to foster a split. You can equally bind unlikely groups into an alliance with each other and yourself if you have a greater interest you both need to solve. Maybe you need to keep a conflict humming but not let either side get too strong or too weak compared to the other. If you're reaping a Red Harvest your goal is to cut down both sides but your interest is in having them at parity most of the way along.
I think it's also a reminder to keep your interests in mind when you make any moves. Is a move satisfying right now but bucks your own long-term interests? Do you have to suck up something miserable to get what you want in the long run?
Games with strict Alignment limit you in this in some ways, of course. I play games without Alignment so it's not a big deal for me.
Hopefully this post was thought-provoking. I don't mean to explore the idea fully here, just plant the idea and get you thinking.
* I first heard it from a Kissinger quote about America, and Charles de Gaulle once spoke a variation, but it goes at least back to this one:
"We have no eternal allies, and we have no perpetual enemies. Our interests are eternal and perpetual, and those interests it is our duty to follow."