I think we have pretty ok lethality estimates somewhere in the ballpark of 0.2 to 0.5 percent.
The lethality rate without care is much higher than the lethality rate with care, and said care often needs to be exhaustive and for an extended period, which can easily fill the entire capacity of hospitals if enough people get infected at once.
Weren't doctors beginning to question whether intubation had any effect on recovery?