Yes I'm asking how the evil feudal lord managed to take over the kingdom when apparently they don't have any evil henchmen to actually facilitate this or help him remain in power. The game MC is the prince the evil feudal lord steals the throne from. You can't even argue that everyone under the MC's command must have been too stupid to understand what they were doing but can't rebel now to keep the kingdom intact because a rightful ruler exists to take back the throne. The people under the MC's command need to be evil or deeply loyal to the evil duke at the very least to get that far but we have been shown that is not the case. Real history has actual details to it so you can see how we get from point A to point B unlike this story.
If you want to write a good story you shouldn't write it so that it immediately casts doubt on itself. It should position itself as this is possible but the means are unknown or mysterious. It's super easy to do that because all you need to do is have the evil feudal lord have a goddamn evil right hand man. Instead what we have is an evil feudal lord with seemingly no one on their side or to deter mutiny in sight because apparently caring about the details of the premise of your story is too much to ask for.