The Equestrians are in a civil war, which does not just stop when a leader dies. A civil war only comes to a stop when all opposing sides in the conflict give up fighting, whether from winning or not. There are plenty of Equestrians that would not want to stop the ones that say they are here to keep them from killing themselves, and currently, you've just gotten through with a war. You've got Triarians after you, Haches, The sarz-guys, and other people.

You are very, very weak. You will not be able to realistically 'gather a giant fleet' that will obey every word. There will be hesitation, there will be disobedience, and there will be severe losses from having to fight another of the Big Three.

Your unrealistically large fleets can't just be summoned. There are damages, there are malfunctions, there are crew losses, and whenever leaders are fighting, there is confusion and people willing to strike out on their own for their martyred, chosen leader.

You don't have an unrealistically large fleet. You have fleets, yes, but not giant ones that will follow all orders.