I spent numerous paragraphs explaining that is NOT how it works. The whole story is about how escalation works. It isn’t about one side saying “I will use nuclear weapons.”

The problem exists regardless of what Russia had said. Even if they had promised to not use nuclear weapons the problem of escalation still exists. WW1 was a good example: What seemed like minor responses at the time led to a domino effect which caused the effects of the assassination of one man to escalate in a horrible world war with gas attacks and horrible trench warfare.