The way we will tell if shutdowns worked is by subsequently comparing them to comparable places that were significantly less closed down.
The length of comparison and the criteria will be important. Perhaps deaths from all causes as a metric and 3 month and 6 month spans. Right now policy makers and modelers have made their best guessed. Let's see what the evidence says later.
To this day nobody knows for sure whether the British bomber offensive in WW2 was a net waste of effort. It seemed to the RAF like a good idea at the time. Expect a similar debate over lockdowns.
