That’s because North Korea knew China had their back.
Diplomacy is simple.
1. Say what you mean
2. Mean what you say
3. Say these things in a form the other culture can understand.
4. Do not lie by either omission or commission but don’t always tell everything you know.
5. Keep agreements or purposely break them but don’t cheat.
6. Treat others as equals
Democrats don’t seem to understand these things.