I'm afraid, Alan, that you are too modern in your thinking. If Dulinor had offed the others, and made claim, he has a *legitemate* legal right to the throne (thank you very much, world's stupidest policy on leader removal). I don't think the fleets would have turned against him, because many of the nobles would have recognized his legal rights and he could justly have called on them to bring the local Imperial forces to heel.
Further, an interesting twist on the story could be this, and we don't know: How many of the nobles on Capital were Dulinor sympathizers? Or just hated Strephon? Historically, many Kings were disliked by their closest rivals for power and those sometimes geographically closest to them (sometimes this was a Machiavellian decision to keep them under the leader's thumb). Having said that, if there were enough people who were sympathizers or just wanted *any* change in management, and if he had managed the 'clean broom' move, even Strephon loyalists would have had no one to be loyal to. At that point, Dulinor looks like the only viable option.
Of course, this won't preclude a few IG die hards taking a shot at the assassin. But that's why Dulinor has his IG. In addition to smuggling in dud weapons for the other gaurd, his gaurd should have brought in some nukes or some other mechanism to inflict significant damage to the local non-Ilelish IG units. They're his most likely threat vector. Smash them, and you're localized threat is gone. By the time an external response can be mounted, you're done and the deal is fait accomplit.
Keep in mind about Capital: Ships are coming and going. But ask yourself this - How much of US military force is present in Washington? Lots of its administration, and some significant force, but relative to the overall force, very little and very little of it the heavy stuff. Similarly, Ottawa, London, Bonn, etc. I think you'll find that in many cases, the core system might well have a lot of police, a lot of military administration, but actual front line combat units might be few and far between. So you shatter the nearby threats, a real response might be hard to muster. Sure, they can call for help... at the speed of jump...
You don't keep good combat units sitting on their hands a Capital. They don't get much combat experience within a few parsecs of your administrative center (or at least not pre-Rebellion!). So you'll tend to have 'security' but the 3I has been so stagnant for several hundred years that it wouldn't surprise me if even that was lax.
Further, an interesting twist on the story could be this, and we don't know: How many of the nobles on Capital were Dulinor sympathizers? Or just hated Strephon? Historically, many Kings were disliked by their closest rivals for power and those sometimes geographically closest to them (sometimes this was a Machiavellian decision to keep them under the leader's thumb). Having said that, if there were enough people who were sympathizers or just wanted *any* change in management, and if he had managed the 'clean broom' move, even Strephon loyalists would have had no one to be loyal to. At that point, Dulinor looks like the only viable option.
Of course, this won't preclude a few IG die hards taking a shot at the assassin. But that's why Dulinor has his IG. In addition to smuggling in dud weapons for the other gaurd, his gaurd should have brought in some nukes or some other mechanism to inflict significant damage to the local non-Ilelish IG units. They're his most likely threat vector. Smash them, and you're localized threat is gone. By the time an external response can be mounted, you're done and the deal is fait accomplit.
Keep in mind about Capital: Ships are coming and going. But ask yourself this - How much of US military force is present in Washington? Lots of its administration, and some significant force, but relative to the overall force, very little and very little of it the heavy stuff. Similarly, Ottawa, London, Bonn, etc. I think you'll find that in many cases, the core system might well have a lot of police, a lot of military administration, but actual front line combat units might be few and far between. So you shatter the nearby threats, a real response might be hard to muster. Sure, they can call for help... at the speed of jump...
You don't keep good combat units sitting on their hands a Capital. They don't get much combat experience within a few parsecs of your administrative center (or at least not pre-Rebellion!). So you'll tend to have 'security' but the 3I has been so stagnant for several hundred years that it wouldn't surprise me if even that was lax.