Common sense

The 5 permanent members of the security council. The UN is a joke when 3 of those members sent missiles into a country none had declared war against as revenge for a chemical attack which never occurred. The only time all Americans cheered Trump (perhaps also the assassination of the Iranian general in Iraq, the one who rid that country of daesh).
How can an organisation be respected when 3 members of a "security" council ignore other countries sovereignty at will? (not saying China and Russia are totally innocent either).

Those are countries are established enough with rational leaders and they realize that everyone would lose.Note Pakistan and North Korea did not join in the chorus.

Their ruling classes are reminding each other.

Or their ruling classes are telling the others who have nukes.

Small non-nuclear proxy wars are okay; only their lower classes die.

They just figured that one out? Not a good sign (It means it's closer than ever)

I'm sure they all mean it. In my estimation, our species will not end from nuclear war. We will soon go bye-bye due to Climate Change.