north-korean people don't have smartphone ?

North Koreans have access to an intranet, which is a restricted version of the Internet containing only sites created by government officials for informational purposes.  As far as we know, no ordinary civilian in North Korea has access to smartphones or any other entirely free device.

Obviously the North Korean government doesn't have full connection with people who live there, so it's irrelevant to whether North Koreans should have access to banking.  If North Koreans ever had access to the full Internet I hope loads of their hands would be on Bitcoin straight away.  For all we know there could already be black markets building there.

It would be much easier for North Korea to launch their own cryptocurrency or online payment processing service controlled by government than embrace bitcoin.
Secondly, these sanctions are not exactly harming ordinary citizens of North Korea, as they are not using banks to transfer money outside the country.

I've always thought it likely that the North Koreans were behind some of the large exchange hacks and even hacks on personal accounts of bitcoin.  It's the perfect crime for them.  I think they were actually implicated in some large hacks on SWIFT itself:

https://en.wikipedia.org/wiki/2015%E2%80%932016_SWIFT_banking_hack#Expanded_scope_and_suspicions_of_North_Korea

(I only perused the OP's article, but I don't believe they mention that)

My guess is that North Korea has massive amounts of crypto from state-sponsored hacks.  It's probably like an industry for them.

Bitcoin is great.

Bitcoin is not a solution for people who are fried alive when they disagree with their government.

North Korea is an open air torture camp and will never start a war because their soldier would need to cross the border and desert immediately LOL.