Tell me why Putin hasn't used nuclear weapons on Ukraine, a vulnerable non-nuclear nation that they are at war with? Is there something uniquely dangerous about

Tell me why Putin hasn't used nuclear weapons on Ukraine, a vulnerable non-nuclear nation that they are at war with? Is there something uniquely dangerous about Muslims in possession of nuclear weapons that you'd like to tell the class? To be clear: Pakistan is a military dictatorship with Sharia Law and Sharia courts in effect for decades, and Islam as their state religion (something that isn't even true of Iran, a country of great religious diversity that's not reflected in Western propaganda). They are as much a theocracy as Saudi Arabia, yet their nuclear weapons aren't an issue because they play patty-cake with Western interests and have no oil reserves for Exxonmobil to salivate over.