Their history was so insular and they never had to learn to get along with another people unless you count the Japanese colonisation and post war US bases.
Now their economy and wealth has far outpaced their cultural and emotional ability to get on with other nationalities in stressful situations.
That said they are nice and polite but I'd shy from working for a Korean company since the way people respond to you is determined by status and some haven't worked out where you stand.
No doubt there are happy stories around too