Vitamin D levels on the Diamond Princess were likely deadly
The worst month for vitamin D levels is February . And the worst demographic for vitamin D levels is the elderly -- and 58% of the 3711 people aboard the Diamond Princess were age 60+, put under quarantine in February.
Why it matters
If you take elderly people in February, you start with the lowest of the low with regard to vitamin D. If you quarantine this group -- this group who already has the "perfect storm" lowest vitamin D ever recorded -- then the vitamin D levels drop even further.
The main form of D in circulation is 25-hydroxyvitamin D, with a half-life of about 3 weeks.
Because quarantine on the Diamond Princess lasted almost 3 weeks, it's likely that many if not most were vitamin D deficient when finally allowed to disembark.
Death risk doubles  when 25-hydroxyvitamin D falls from 21 ng/mL to about 10 ng/mL -- which may represent a plausible but unlikely best-case scenario for the Diamond Princess.
More probable is that death risk tripled or quadrupled.
If most were vitamin D deficient, then even plain flu could have attacked the Diamond Princess and resulted in more than a half-dozen deaths.
What that means
It means the best available evidence we have (the Diamond Princess data) indicates that COVID-19 is not worse than flu -- and that we're "being played" by politicians right now.
 Vitamin D (25OHD) Serum Seasonality in the United States. PLoS One. 2013; 8(6): e65785. Available: ncbi.nlm.nih.gov/pmc/articles/PMC3689782/
 Relationship between 25-hydroxyvitamin D and all-cause and cardiovascular disease mortality. Am J Med. 2013 Jun;126(6):509-14.
doi: 10.1016/j.amjmed.2012.11.021. Epub 2013 Apr 17. Available: https://pubmed.ncbi.nlm.nih.gov/23601272/