You cannot blame Kim Jong-un for flexing North Korea’s military muscle when Biden is recklessly saber-rattling with Taiwan and China. How does Kim know the US will not also team up with South Korea for an invasion of the North? Trump's relationship with and policies towards North Korea maintained stability in the Korean Peninsula.
Kim Jong-Un's geopolitical actions have been erratic, and his missile launches are destabilizing the Peninsula. Instead of provoking a confrontation, Kim should take the Biden administration up on its offer to meet without preconditions, and settle any of his grievances peacefully. Biden is showing strength and prudence in the region.
There's a 17% chance that North Korea and South Korea will be recognized as a single sovereign state by 2045, according to the Metaculus prediction community.