As a blame-free explanation of why SARS-CoV-2 become so widespread, I think the parent comment is basically correct. From [0], "SARS, caused by a respiratory-

As a blame-free explanation of why SARS-CoV-2 become so widespread, I think the parent comment is basically correct. From [0], "SARS, caused by a respiratory-tract virus, also failed [to become a pandemic], although it came close to causing a pandemic after its emergence in late 2002. It killed almost 800 people worldwide, but was rapidly stopped mainly because infected people developed symptoms quickly." In contrast, Covid-19 spreads pre-symptomatically, and infections are frequently mild or asymptomatic. The test-trace-isolate containment strategy, such that it was, relied on people acting in response to symptoms. People without symptoms can't do that, and if someone has what feels like a normal cold they're just not very likely to take special precautions, at least early on when the disease is rare and there's still a chance of containment. The pandemic response we prepare for next time needs to compensate for this, such as by adopting proactive disease surveillance or increasing efforts in other areas. As for the pandemic not being that bad, we did get lucky in a couple ways: it was possible to rapidly develop many vaccines, and the mortality rate was relatively low. Covid, disturbingly, was sort of the least bad version of a global pandemic, at least compared to the alternative scenarios outlined in warnings (e.g., [0]) over the past several decades. [0] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2002527/ https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2002527/