Thanks to Boho  for suggesting to collect these comments.

Can Zi Ang's narrative be trusted? Did he invade to "help"? (by river11)  


Duan Zi Ang is not the best reliable narrator of his reasons to colonize, destroy and to strip its people of their land. 


In ep 9 Zi Ang has a mini breakdown when confronted by Shu He of the destruction and death he caused to his people. He was in denial of the reality, I mean has there ever been a country takeover peacefully? 
never, colonization brings death and destruction. Zi Ang represents what most colonizers believe, that for your own good, I will save you etc. This imperialistic ideals have been used over and over again to invade others, when, in fact, they enrich themselves, like the North did with the salt mines as an example. 


Admittedly, Shu He was not a good ruler but is poverty and poor ruling an excuse to invade another country? That is the excuse that Zi Ang uses to get him and to fulfill a long standing goal of the North. Zi Ang was a trained assassin and a politician he could have done many things to get to Shu He and help him in other ways. The fact that he started to built the mansion and trained the maids to make South Hui tea, re-affirms my belief that he just wanted complete possession of Shu He and his plan to attack started the minute they parted. There was no resistance because they were overpowered by a great army, lack of resources not because they didn't want to fight. who gives up their land willingly? however, the people go into survival mode and would welcome the enemy! 
I think Zi Ang died not understanding his touch of madness, he stripped Shu He of his freedom and personal agency and the last thing he says is that Shu He lied to him his whole life'. I think Shu He knew his kingdom was in trouble but was powerless to change it.


Was Shu He really an incompetent ruler? (by Yerisina)

In a way, yes he was, but I want to reiterate that he also never stood a chance. And here is why I think so:

Lack of political experience coupled with his idealism
Shu He was intelligent and literate, which in theory at least, should be considered good traits for a ruler.
However we know he had little experience - and like anyone learning a new skill, he would have needed someone to guide him. Someone he could trust.
Another one of his traits, his kindness, while admirable, may have worked against him in a political environment. Because harsh choices, such as warfare, and punishment, are sometimes necessary. Politics is a world of power structures, competing interests, and tough decisions, something he never was cut out for.

Deep- rooted corruption in South Hui
Prime Minister Gu:
- manipulated Shu Qian
- pushed for Shu He to join the court to further his own ambitions
- used Shu Qian for the massacre of the Duan family
- was possibly even being involved in the death of Shu He’s mother
In essence, a man who stops at nothing. And yet he was the one who Shu He had the "best" connection with among all ministers in the court.


Other Court Members
While we don't know as much about the other ministers, it’s safe to assume that they were no better than Gu.
In Episode 4, Shu He comments to Zi Ang, "The ruling and opposing factions of South Hui are intertwined. They've been rotten for a long time. On the surface, it looks prosperous, but up close, it’s all made up of white bones that can’t be shaken."

This reveals that corruption ran deep, and even if Shu He had wanted to take action, his ability to do so was severely limited by those around him.

South Hui was weakened before Shu He became emperor?
- When Shu He enters the court, his father just accepts North Ji‘s higher taxes —> less money
- The engagement to Princess Wen Jing —> a strategic move that would have benefited weaker South Hui, even if it came with its own drawbacks


During Shu He‘s reign
The drought likely impacted the kingdom's finances.
Diplomatic Isolation was probably a bad move. However, was this due to his personal feelings toward Zi Ang, or was he manipulated by his ministers?

As revenge for the death of Shu Qian at the hands of Zi Ang, the ministers pushed for an attack on North Ji. Shu He rejected the proposal, potentially because of his lingering feelings for Zi Ang? Or because of a reluctance to engage in unnecessary bloodshed? Either way, the ministers were probably furious.

The impending rebellion
Rebellions don’t topple rulers just because the people rise up; they usually succeed when the power structures that support the ruler (like the military, elite classes, and bureaucracy) have already abandoned them.

Signs of competence?
A scene that stuck with me was when Shu He accompanied Zi Ang to court. He immediately knew how to navigate the situation, when he suggested to give them access to South Hui‘s salt mines.

Conclusion
Shu He’s downfall was not simply due to incompetence. He lacked the political experience, the ruthlessness, and the trusted allies needed to navigate the complex power dynamics. Competence in politics isn’t just about what you know or what decisions you make; it’s also about the ability to build and maintain the necessary networks of support. Because no man rules alone. In this respect, Shu He never had a chance.

I highly recommend this video, if you haven’t seen it yet: Rules for Rulers
https://youtu.be/rStL7niR7gs

Yeyyyy .. you did it finally. Amazing analysis. 👏🏻👏🏻