There are two main reasons for the North Korean regime's continued survival:
1. Most of their neighbors are afraid of what might happen if it collapses.
2. The CCP likes having it around, both to act as a junkyard dog and to keep America and/or South Korea from establishing a military presence near the Yalu River.
The latter ties in to speculation I've heard that Beijing may have ordered Kim Jong-un's assassination because they thought he might've been moving towards warmer relations with America, South Korea and Japan.
Then again, North Korea's state media
recently said Kim Jong-un appeared in public. But he's known to have body doubles and Norkie media doesn't exactly have a track record for honesty, so I'm taking this with a grain of salt.