What did Yongle do for a living? Is this reason involved with why he is important? Why did he(they?) become an emperor?

As I mentioned in my other articles, Yongle was an emperor. Or should I say they were emperors? But that's an entirely different article I've written about. Let's get back to this one! So I've already told you what Yongle did for a living. And yes, of course his was involved in why Yongle is important. But what I haven't told you is why the Yongle emperors decided to become emperors! Well, the Yongle were emperors because they of course inherited the throne. Some of the Yongle emperors had to compete against their brother's for the throne. One Yongle emperor even declared himself king after his fathers death, even when it wasn't his turn! I would be pretty mad to be the brother that was supposed to inherit the throne of my father!