The summary statistic leaves out the effect of age. Most of the non-overweight people who died were old. The main reason you'd die of covid if you are young is being overweight or obese:
> Patients with BMIs greater than 40 kg/m2 had higher death rates overall, and those with BMIs greater than 45 kg/m2 had a risk ratio of 4.18. Most strikingly, however, those younger than 60 years had increased risk ratios of 12 to 17 versus 1 to 3 if they were older; high BMI increased risk in men more than in women.
> Patients with BMIs greater than 40 kg/m2 had higher death rates overall, and those with BMIs greater than 45 kg/m2 had a risk ratio of 4.18. Most strikingly, however, those younger than 60 years had increased risk ratios of 12 to 17 versus 1 to 3 if they were older; high BMI increased risk in men more than in women.
https://www.acpjournals.org/doi/10.7326/M20-5677