The higher ups, not sure of the correct term but like his government, love him. He's an emperor who is strong, feared and is taking over the world and they believe in him and his ways. The philosophy being, don't piss him off and you'll be fine. Even the Chamberlain (i think that was his title?) was literally stabbed by him and he still was on the emperors side. Tyrants create great councils of yes men. It's probably the most realistic aspect of this story sadly.
Raon could have taken over probably, but he didn't want to be emperor. they'd have figured it out if he'd actually died but they liked him or he'd have been assassinated already.
As for other nations trying to overthrow him, think genghis khan, cities and tribes would surrender as he arrived to avoid the bloodshed resisting would bring. No one defeated him, he died on campaign and it was in-fighting between his sons that stopped the mongol empire spreading further. This is the kind of emperor Garon is.
Sorry for the history lesson
He might be tyrant but not stupid one garon is very smart never left his palace work for later always does things on time he is tyrant for imaes but not for common humans he also supervise his empire himself in disguise to see what's going on in his empire makes him a emperor who cares about his people since he expanded thd Empire himself and hold this position intact no other person can do it so they depend on garon a lot that's why no one took his place.
It's complicated and complex feelings roha has towards garon it's not love in novel why it consider why brother isn't end game cuz roha thinks my hatred overlap with love he is grateful to brother for saving him treating him best but he feel brother deserve better and I m not, that my heart which is complex with hatred towards garon is more than love he wants to feel with brother and hatred with garon this storyline author made like villain won hero lost , i also at some point thought yah brother lost everything in exchange roha let brother name him even though garon wouldn't like it ...... But you can say yah it's stockholm syndrome but roha slept with garon willingly to let toxins consume him but even at the last breath of it garon knew about antidote didn't left good taste inside roha in novel he was like "you knew everything from the beginning you let it happen knew about antidote were my horn what's the point of killing man who is dying in front of me willingly " hence he gave him his horns. ....... I feel if he hadn't end up with garon story would be sad and many readers wouldn't like it i mean garon left big impression compared to brother on me or may be to many readers may be novel suspense would be whom roha would choose

Can someone help me here? I understand that they didn’t kill Garon but they invaded his palace no? They didn’t dethrone him? I thought it was all over, they had him cornered. HE KILLED BOTH OF THEIR MOTHERS. So basically nothing happened but my poor baby’s Horn is now missing because he chopped it off. I’m a bit disappointed. atp there seems to be no clear end.