Russia is turning North Korea into its agent of mischief

There are good reasons why Russia is expanding ties with North Korea. As the TASS report states, there are economic opportunities to be had. Russia would like to sell electricity and natural gas to South Korea, and both will have to go through North Korea. North Korea also has
trillions in mineral wealth
it needs capital to exploit.

There are also bad reasons.

Russian President Vladimir Putin is bent on restoring not only the old Soviet Union’s borders, but its sphere of influence and client states. States such as East Germany and North Korea were particularly useful in they insulated the Soviet Union from another World War II-style attack.

If you view Russia as continually under threat, as Putin and his allies do, you want the protection of those satellite nations back.

Russia is also looking for an Asian provocateur.