The buzz is that this test differs from the 2 previous attempts in that this one is an enriched uranium device rather than a plutonium-based implosion device.
The Uranium device is much simpler, and is almost impossible to screw up. It also uses expensive bomb grade uranium, which requires centrifuges spinning for years to accomplish and provide a rather low yield. Plutonium is a byproduct of a fast breeder reactor, and is easily separated, MUCH cheaper to acquire and has a much more significant yield and can be enhanced to improve the yield.
That said, This device would not be prolific due to the enrichment process.
This test was to prove to the world that they are significant. Another failure would have been disastrous for the leaders of this Prison Camp masquerading as a country.
I like that description.