Sorry I'm late to this.
Nexon was never an issue with CoH/V's closure. Nexon had no say in the day to day running of the company.
The original stock purchase was part of an agreement to form a joint studio, N Square, and allow each company to pick the brains of the other. NCSOFT learned how to monetize games better with a cash shop as well as mobile games and working with a partner in China and Nexon got to look at how you develop a real 3D MMO.
Of course what happen was N Square joint development got derailed, a very similar game was announced by NCSOFT a month or two to one N Square was developing which was then cancelled a month or two later (N Square version). Also after 2 1/2 years since the stock purchase, NCSOFT stock value never recovered leaving Nexon with a huge paper loss so they tried to take control of NCSOFT to push the stock price up. NCSOFT out maneuvered Nexon and after the courts told Nexon that how NCSOFT did it was OK, Nexon got out and took the $150 million loss.
Now the only person who made out was NCSOFT's founder and CEO. It was his personal stock that was sold to Nexon, so he got the $685 million and after Nexon sold off their share, bought back a portion at a reduced cost making him once again the largest single stockholder.
So the end of this "marriage" NCSOFT finally entered China with their IPs, Lineage is making more money than ever due to it's cash shop, and NCSOFT has a new MOBA/fighter like title coming out as well as a slew of mobile games. And Nexon got a harsh lesson in investing in a competitor with a crashing, over-inflated stock price.