The story told to the general public was obviously not the story to be closest to scientific truth, but instead the story that was thought to lead to the least severe outcomes. Nobody really knew the real fatality rate last year, the numbers could range from more than 10% to about 0.1%. If they turned out to be about 10%, quarantene would be essential in stopping the spread of the infection. Also, higher fatality rate would mean that the infection rate would be relatively low (as the number of dead were known), meaning that it would be realistically possible to exterminate the virus. On the other edge of the spectrum, the fatality rate might be near 0.1%, but the infection rate would be much higher. If this held true, flatting the curve would actually be a good strategy. Finally, if the true fatality rate would be around 1% (roughly the real number), the one would "flatten the curve" until a vaccine could be provided, as if hospitals had been flooded way behond what has happened, the fatality rate could easily be 2-4x higher. In the case of the US, that could mean around 10 million dead by now, if no lockdown or social distancing had been attempted.
Of course, had no action been taken to slow it down, and millions had died last spring (in the US alone), the public opinion would strongly demand a lockdown, as well as become so scared that they voluntarily self-isolate.