Woah, woah, woah. Who ever said intra-realm conflicts need to be conspiracies, which is what you seem to be suggesting. And while, yes, realm-wide conflicts involve more people, most of that is just moving to or from some position, refiting, or waiting for the army to rally at a certain point. Let's face it, unless you are besieging a city/stronghold, you may be part of a battle maybe once every week. If you are lucky and your realm is right next to the one you are fighting.
An intra-realm conflict can simply be two groups in the realm that each have their own goals. This can be secretive goals, as you are suggesting, or simply a matter of policy when it comes to foreign outlook. It can be as bad as civil war, or just an heated discussion between two groups of nobles over who can do what when.
If there's a faction that strongly feels attached to ideals you strongly oppose, and they are too strong to simply push aside, then odds are you will start conspiring against them. I've gone down that path, multiple times. Since odds are parties on both sides have the capacity to substantially wreck the realm (otherwise, you'd just push them aside), you are likely going to have to think of a secretive plan to outwit them and deal with them for good, so that they stop "corrupting the honorable realm" as you envision it ought to be. You'll want newbies, sure, but not really as anything more than pawns. You give them a few tidbits, make them feel special and lecture them of the evils of the other guys, and you've secured their loyalty. It's what I did, at least, and what was basically done to myself before that. Then again, those were some of my best days in the game.
On the other hand, not everyone needs or bothers with lackeys. Some just need time for their plan to work out, they are waiting for an opportunity. If they don't need lackeys, they might not bother risking exposure by getting any. I've also had my share of silent intra-realm feuds, and they were so silent I think the targets never even realized it. These kinds of intra-realm conflicts hardly involve anyone and don't result in anything spectacular.
I disagree with your stance that inter-realm conflict is just following orders. They can just as much be secretive and public as intra-realm conflicts... So really, I'm not saying that intra-realm conflicts must be secretive and inter-realm conflicts involve a lot of people, I'm just saying that's your typical scenario. I've seen my share of young players really immerse themselves in crusades, all too eager to badmouth the heretics when we finally meet them in battle to call out their cowardice and heresy. I've also seen my share of decisions on what to do, with who, when, and how being fully discussed in public and involving a great many people in the decision-making. And while you might just feel like you are pushing a button to set travels when following orders, I do remember my early days and occasionally do see that flame in new players' (and sometimes old players') spirits: they aren't just clicking a few links, they are am active force in a lively struggle. They really do care whether or not a lot of their peers will move with them, how many of their troops will die in battle, and how well the war is going. When one is really attached to his character or his realm, this sort of immersion comes easily.
Furthermore, let me say why I believe that intra-realm conflicts create more secrecy. Simply put, in my experience, those realms that involve as many people as possible in public discussions were the more homogenous ones. In order to assure social cohesion and to maximize fun for everyone, it is very much in their own interests to do so. However, the divided realms are often forced into greater secrecy. I think of the monarchists and republicans of the old days in Fwuvoghor, notably. Each faction had its own ideologies, strong personalities, religion, friendly realms, etc. While the republicans were generally pro-Riombara, the monarchists were generally pro-Enweil. When the invasion hit, the republicans were more pro-monsters, the monarchists pro-undead. As such, you can imagine that if a faction went out to make deals with outside parties (whatever the ends), it was usually in their best interests to keep it to themselves, either by telling nothing of it or skipping the specifics. Especially since many of these actions could try to lock the realm on a certain faction's path, and the details of which were likely morally reprehensible to them.
Now while this conflict did end up generating a lot of excitement for many, as both factions were dead-intent on converting new blood to their cause, I've seen many more cases where this was not the case, where a clique of people, often but not always with OOC ties, decide to get together to get their way and therefore decided to only rely upon people they can trust OOC. People outside of these circles can often not hope to ascend to anything, whatever their aid to the clique.
I'd also like to point out that I've seen at least two, if not more people, leave a realm, delete their character, or the game because of how chaotic everything was. Obviously, even if people from both factions were having an OOC blast, this sentiment was not shared by everyone.
I honestly have no idea what my point is... Food for thought, I guess.
