Sanctions don't work. Syria didn't collapse because of sanctions, but because of a very long civil war and, more importantly, a sudden imbalance in external forces (Russia was preoccupied with Ukraine). I don't think there has ever been a case where a country, or its people, changed the regime because of sanctions. Never. North Korea, Iran, Cuba, Palestine, and much of Africa are examples. Wars and revolutions change regimes. I would even argue that sanctions help regimes stay in power. When an external force imposes a threat (sanctions) on people, those people don't see the outside as "saviours" but as an enemy. They often resent the country that imposed the sanctions more than their own government, and they have no desire to fight an external enemy on behalf of a domestic dictator.

Sanctions punish ordinary people, many of whom are already suffering under the regime. So they end up opposing both an internal and an external enemy. In the long run, sanctions probably destroy and cost far more lives than wars. It's a sadistic way to try to crush an enemy.