What if this coronavirus were 10 times more deadly? 20 times? What if it hit all ages equally, or was especially lethal to young adults ( like the 1918 flu)? What if it crippled, like polio?
Would people in those hypothetical scenarios have been as crazy as they are now,? They are not impossible: the idea that natural selection tightly limits possible virulence is not correct. In the famous misapplied example, myxomatosis, virulence in rabbits dropped from > 99% to ~ 50% – but I wouldn’t quite call that having a cold. And it involved selection acting on the rabbits, as well – old-fashioned rabbit strains exhibit much higher than 50% mortality when exposed to current strains of myxomatosis.
I don’t believe that there’s a reserve supply of sanity that is called out when it’s truly needed. Not this year, anyhow.