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.

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.