First, sanctions on Iran have zero to do with its authoritarian government - the US has no problem selling to authoritarian governments - but rather the geopolitical conflict stemming from a slew of lovely US actions such as overthrowing the democratically elected leader of Iran and installing a repressive and brutal dictator which destabilized the country to a degree that the events of 1979 and after were possible.

The efficacy of economic sanctions is complicated and debated, but one can absolutely say there is little compelling evidence that they result in positive outcomes for anybody.