It does seem to be a Chinese tradition (and I believe in quite a few other places) to pacify the old king and grant them a comfortable enough retirement, as the

It does seem to be a Chinese tradition (and I believe in quite a few other places) to pacify the old king and grant them a comfortable enough retirement, as they’ve already lost power. It’s probably less confrontational and somewhat satisfies all sides in the long run. Examples would be some kings during the Three Kingdom period, who all got some sort of honorary title in the conqueror’s kingdom.