There is some evidence, as we've seen, that moderate Vitamin D supplementation helps to protect to an extent against the worst effects of Covid.
But I still don't understand why those who want to take something to protect themselves are unwilling to take the obvious and best protection, which is the vaccine.
In my case I mentioned it a few posts back.
1) My experience is that since I have had optimal Vitamin D levels I have not caught colds and such (which is often reported by people who go on to optimize their vitamin D levels), and there is evidence to suggest that the same would be true with Covid.
2) I was more reluctant when the vaccines first came out. The more time passes and I see that there are no widespread negative effects, the less reluctant I am.
While you seem to have put a lot of coincidental information together, I get the feeling that you are attributing to malice that which can be adequately explained by "accident". Since the beginning of the human species, our body has been able to produce vitamin D from sunlight or receive it from sources like eggs. In the modern world, with many people choosing to stay indoors and hooked on TV or the internet, it is a natural consequence that people are getting less exposure to sunlight. Same with food sources, people are increasingly under pressure from work and home cooking has taken a back seat, many healthy foods are shunned in favor of fast food. Now, the only part of your idea that is possibly true is that artificially created supplements might be unnecessarily expensive, but this is also driven by supply and demand. If you combine all these shifts in human behavior it is easy to see people getting less vitamin D than the past few decades, but to call it a conspiracy when it is simply self inflicted collective societal changes seems a bit silly.
Our behavior by making more life indoors is not due to a conspiracy. The recommendation not to sunbathe and when we do sunbathe we put on supposedly protective sunscreen is what could be due to a conspiracy.
I can't be sure if there is a conspiracy or not, but after years of reading about it, it seems to me the most likely hypothesis. Besides, as in other subjects, I am open to strong arguments to change my opinion.
And it's funny that you mention the food issue. It is precisely another conspiracy that I believe in. Coca-Cola McDonald's and a lot of companies paying experts to convince everyone that it is the same to eat 2.000Kcal of Coca Cola and McDonald's than 2.000Kcal of broccoli with salmon. Also that healthy is to eat a minimum of 5 times a day, when that is a barbarity that has never been done in the history of mankind in places where there was plenty of food.
So here we are, with obesity levels and chronic diseases breaking records every year.