because it is in China’s interest not to have more nuclear capable countries, especially one right next door?
Sanctions are pushing nations to turn to nuclear weapons, only security guarantees stop them. Anyway, north Korea is a nuclear weapons state now. A poor, unstable nuclear power means a lot more risk than a stable, wealthy one. If China had really wanted to stop North Korea from developing nuclear weapons, then China should have more clearly reaffirmed its commitment to fight for north Korea if it gets invaded. Same for Iran, sanctions lead to the opposite outcome of what is the original intention. That should be pretty obvious by now
To avoid sanction on herself?
How did that work out?
because they provide little potential returns?
And investing in Argentina or burning money in Pakistan is profitable? Countries that have been starved of capital are the ones that give the most return when they get access to capital. Quite a lot of BRI projects are more political than purely profit driven
Because China is concerned with actually developing and not making spiteful symbolic gestures to please a few foreign observers.
Powerful allies are not symbolic gestures. And if China had spoiled sanctions before, the west wouldn't have bothered sanctioning Russia and China itself as much as they have. Sanctions are being used because the west believes they work.
China didn't enter the Korean war to "have a rich friend", it entered the Korean war to evict US troops from Korean peninsula, or at the very least, establish a military buffer zone.
The criteria for whether a military ally is a success is determined by whether it's still alive, not whether it is rich. All other criteria is nice-to-have, but not necessary for a successful alliance.
The purpose of a military ally is a means to an end (armed reunification, evict US troops out of East Asia), not to brag about having rich friends.
The war happened a long time ago. Sure, it's a success that North Korea survives. But wouldn't it be even better if they were a bit stronger and didn't need as much help? Wouldn't it be useful for the northeastern provinces to have a nearby trading partner? Currently, North Korea is always close to collapse just because they are so poor. What's is China gaining today from keeping them poor?
So why do countries even bother talking to China, or why did China even bother stepping onto the world stage? If all developing countries want are weapons to defend themselves China could've just let Russia take up the heavy slack of uniting the global south, while China saved all its money for home. As for your last sentence, hahaha Vietnam in 1979, regardless of whether you think China won or lost that war, would like to have a word with you.
China had a powerful army after the civil war and then developed nuclear weapons. After security was established, the economy could take off. Of course only countries that are under constant threat of invasion or bombing are forced to put security above economics
Arguably China couldn't conduct a larger war against Vietnam because of the threat of a Soviet invasion from the north. And the Soviet Union didn't enforce sanctions against countries that wanted to be its allies.
We are today in the absurd situation that countries fear American sanctions not because of the US markets but because China enforces American sanctions even as there are new sanctions on Chinese companies every week