The UN report is right about the North Korean hackers. Most of the North Korean hackers find it as hobby to hack crypto users and exchanges because no one is there to stop them. $750M is not a small amount and it can't be done without support from a government.
The North Korean government doesn't take any actions against those thefts and that's why the malicious actors get more courage to do such crimes. When government support is in your back and criminals get rewarded then in a country like that everyone will try to follow the same path.
It's not a hobby!
It's a state operation, all the hacking is on the orders of the government, all the hackers are employed by the government, their moves are also tracked, and they don't make one penny from their hacks, all goes to the government.
You can't be a hacker in NK without the government knowing it, as you won't have internet, you will have an intranet, named Kwangmyong, and is not possible to access anything outside it (from the world internet through it), and it only officials have access to the real deal.
So all those cases of stolen cryptos are actions supervised and controlled by the NK government itself, not some rogue hackers who if they would try such a thing in NK would get 100 bullets in their head the next day without a trial.