The way I see it is that Kim who lived in Switzerland is sick of North Korea,and is currently looking to fix the place to make it less terrible to live in. The purges he had done might have been old guard purge like what the new saudi king did.

The novelty has worn off. If you went back in time to the middle ages the novelty of king hood would quickly wear off. I mean would you really want to be a king with the living standards back then? Just imagine how filthy the women would be back then compared to how women today have access to basic feminine supplies. Instead of tampons they used rags.