North Korean leader Kim Jong un (C) plays with children during a visit to the Taesongsan General Hospital in this undated photo released by North Korea's Korean Central News Agency (KCNA) in Pyongyang May 19, 2014.
[WDW]Megaraptor provides a short summary:
Kim Jong Un grew up in Switzerland, has no friends in the North Korean government.
All real power in DPRK is held by a group called the Organization and Guidance Department (OGD), made up of associates of his father Kim Jong Il. When someone was admitted to the OGD, they were considered to take on some aspects of Kim Jong Il's divinity.
The execution of Kim Jong Un's uncle eliminated the last real threat to the OGD's power, now Little Kim basically has to do whatever they say.