>>507584304MAD doesn't work. Quite the opposite, in fact. By disabling both countries from wars of instant annihilation, MAD forces a stalemate that allows for stockpiling of conventional arms. Just look at Ukraine. Nobody can strategically destroy Russia and that enables their aggression.
Also, Iran always acts via proxy. They can let a few nukes slip to terrorists and then it's game over.
As soon as they made that ICBM attack last year, their fate was sealed.