But also, isn't there an agreement that any house that uses nukes against human targets gets obliterated by the entire Landsraad ? Which might make a bit problematic the Fremens' use of nuke(s) in the Lynch-version assault on the emperor.
I think you're correct. It's been a while since I read the books and I deliberately didn't reread them before the movie to avoid the kind of frustrations that occur when you see an adaptation and are too-familiar with the books so a few of these details are escaping me at present.
The Fremen in Lynch's adaptation did what they did in the book. They won the war any way they could as they were the underdogs, without taking Arakeen they couldn't win it.
Except that others will use it against you. Also, because this movie didn't convey it well, Spice is literally the thing that keeps the Empire and the economy going. Without it, there is no interstellar travel (thanks to a religious opposition to thinking machines). So maybe on an arbitrary barren sand planet you could try and get away with it, but this is not the one you want to test that on. It would be tantamount, at the time of the book's writing, to nuking the OPEC nations on Earth, you know, the places where (at the time) an incredibly large percentage of oil was being pulled out of the ground and keeping the global economy going.
I should probably just stop here and not expect to grok the geopolitics of this universe over a conversation like this but...
* Why is there so much conflict if there's an empire?
* Why doesn't one faction simply control the planet?
* These are just regular nukes right? Like on the scale of the atomic weapons we have now? I guess on the scale of intergalactic conflict those don't sound very important to me? Very different from the scale of a nuke on an OPEC state city.
Why is there conflict in any nation with an existing government? Because people have desires which conflict with the status quo. They want more power, more resources, better resources. In a galactic empire, do you want a planet or the best planet? Do you want the planet that makes you the most wealth or the planet that's just a bunch of rocks?
The Emperor, ostensibly, controls all the planets. The political system is based on fiefdoms in the book. He hands the administration of Arrakis to a particular noble based on his own political objectives and trust.
They are essentially nukes, yes. But melange (the spice) is only available from Arrakis (in the books it's discussed that they try and find ways to make it elsewhere, but without spoilers I can't so much more than that it doesn't work). If the OPEC nations were your only or principal source of oil in this world, and you nuked them, what immediate impact would you expect from that? A global economic shutdown, and almost certainly being ostracized (if not worse) from the international community. Setting off nukes and making it practically impossible to export melange from Arrakis would be similarly effective at collapsing the galactic empire and economy.
OPEC doesn't feel like the right analogy. OPEC is a foreign state. Arrakis seems to be, like all planets, owned by the galactic empire. It is by several orders of magnitude the most important planet. A better analogy would be if, say, Hawaii, contained the bulk of the world's energy resources. It is strange to me that the galactic empire doesn't rule this planet directly with extreme security measures. Why isn't the empire immediately taking charge directly when there's any sign of conflict on the most important place in the empire?
You're reading way too much into my analogy, but sure, go with your Hawaii version. It's an analogy, they are not exact, just, you know, analogies. To give you a sense of the idea.
Why not? You'd have to ask Frank Herbert for a definitive answer, but the next best is to read the books. There are many factions involved, the emperor is not actually in a position of absolute authority. The Great Houses, the Spacing Guild, Bene Geseret, Bene Tleilax and others also wield influence. There are checks and balances in place (by custom, by law, by force), and one of those is that the Emperor does not control Arrakis directly. It would put him in a position with too much power that the others (envious or desirous of semi-selfrule) would object to, probably violently. Arrakis is also a source of great wealth, and by giving it out to specific Houses, the Emperor is granting a favor (at least on the surface) and buying their allegiance.