I think based on the studies linked in the source above quite a lot of what you've stated as plain fact is easily debatable.
1. Does not seem like Vitamin D supplementation provides any of the benefits that are linked to Vitamin D from sun exposure.
2. The maladies strongly linked to being combatted by said Vitamin D kill far, far more Americans (700,000) than melanoma (7,000) a year.
3. Obesity and vitamin D have a pretty strong experimental link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5691711/