I chose one at random, it didn't explain an underlying mechanism why vitamin D might have such a large range of health benefits like you claim.

It is quite easy for an organisation to p-hack. It's also quite easy for an organisation to ignore correlation vs causation.

So I was wanting to know in summary (a blog is fine) what the underlying mechanism is to which vitamin D could solve so many problems.

[edit] I'll add an article critical of your way of researching - https://www.healthnewsreview.org/2017/03/vitamin-d-cancer-ho...

Your own self-serving bologna doesn't count as well-established science, and making unfounded health claims about supplements is illegal under numerous federal laws. I suggest everyone reading this contact the FDA to urge enforcement action against these shylock clowns.