> If you quarantine and the virus is controlled, then it looks like you panicked over nothing, because you took this huge reaction and nothing much happened. However, if you wait till it's sufficiently bad and then you quarantine everyone will understand what you did, and later, you may get praised for your decisive leadership in a time of struggle.

This need not be this case. Any authorities who take action to shut down social contact now, before they turn into Italy, will be praised several months hence for being forward thinking because it will be clear what happened in every jurisdiction where they didn't shut down social contact, i.e. absolute catastrophe.