Why would people create these elite soldiers out of slaves and give them that much power? Well, the answer is they were the safest people to give power to. Remember, these empires are ruling over many tribes and many groups and many kingdoms that are constantly vying for power, trying to establish their own dynasties. And if you allowed people from those various tribes to protect you as emperor, well, there might be a good shot that one of them might wanna kill you and establish their own dynasty. But from a young age, if you could indoctrinate these young boys as gulams or as janissaries, well, they might be more loyal to you. And indeed, it did provide an unusual amount of stability. As I mentioned, the Mughal Empire was able to be founded by Babur who was Timur's great-grandson's grandson.