I'll start at the beginning to try to explain how my worldview is different from many people here.
The treatment of the topic in this article appears to assume that simply by labelling these beliefs as conspiracy theories, they are disproven. Why else would beliefs that are held by such a large portion of the public apparently be dismissed out of hand? There is no other explanation given. They are labelled as conspiracy theories and therefore are not true by default.
In my very different worldview, describing these ideas as "conspiracy theories" makes me suspect even more that at least some of them may have an element of truth. Because historically that description has been used for many government actions that they wanted to cover up.
So in my worldview, even the term "conspiracy theory" is potentially a manipulation, and a significant number of conspiracy theories are true instances of government malignment. Normally many of these are acknowledged to some degree up to a certain historical distance. So if you are interested then you can research further to understand my point of view better.