The world powers care less about a possible nuclear holocaust caused by Iran and more concerned about profits. Russia is selling the s-300 defense system to Iran, that might turn around in the future and kick them in the ass. If Chechens get hold of a bomb from Iran and blow it up in Russia, then Russia will retaliate by trying to bomb Iran and their jets get blown out of the skies with their own weapons. China is more worried about disturbing their oil supply than keeping the world safe from Iran. The USA and the EU are feckless in their demands for sanctions that really bite against Iran. How about an air ,land and sea embargo against Iran as starters.
U.S. envoy to UN visits Cuba's UN Mission, a first in decades (AP)
from the article: Russia to supply Iran with S-300 defense systems