To see a conspiracy, we have to interpret some pattern of activity as the intentional design of a small group to gain some advantage. There are pitfalls in this.
We might be see cause where there is only correlation. This same mental shortcut leads to other theories, like "The Invisible Hand of the Market," which is invisible because it's not there at all, and "Intelligent Design," the idea that the very organization of the Universe proves the existence of God. The standard counter-argument is that the Universe is a self-organizing system. The only reason this could possibly matter to humans is that a Designer of the Universe might be aware of us, so we had better watch our step. And maybe we can cut a deal. And that view pulls for some hasty conclusions when we get suspicious about anything.
We might infer that we're smarter than the conspirators. If we weren't smarter, how would we even suspect? This is very ego-friendly stuff. That alone should be a big red flag. My favorite rule of thumb is this: You won't hear the one that hits you. A really dangerous conspiracy will not be one we can identify.
How does a real conspiracy get found out? Has a conspiracy theory ever been involved in the bust? Insiders or professionals with direct knowledge, blow the whistle, or make a mistake, or there's some kind of audit, and the whole thing falls apart. I can't recall any popular theories ever leading to such an outcome.
A person who takes down a conspiracy does so at considerable personal risk, and usually suffers severely for their courage. I do recall working with such a person several years ago, who had been a top bomb specialist with the FBI. His work was hard science: the data either linked the bomb to the accused, or it didn't. He was involved in the (pre-911) WTC bombing, and was kept away from the Oklahoma City bombing, where his expertise would have been of critical value, after giving true but exculpatory court testimony in the WTC case. He was subjected to reprisals and eventually fired. After his departure it was learned that the FBI had falsified his reports for clueless hired "expert witnesses" in court cases to help prosecutors. There are books about this episode.
Most conspiracy theory writing I've seen, including some very skillfully presented stories, don't rise to the level of yelling "boo" or "yay" from the bleachers at a ballgame, for all the impact they have on the purported conspiracies. They call attention to the writer, get a few people excited (like an old guy who rides a bicycle down the street talking to himself about the Illuminati) and probably play into the hands of some PR firms with fat pre-election contracts.
I was in India when the Gates people were reported to be very active in the vaccine testing business, and two weeks later I was totally paralyzed with Guillain-Barre' Syndrome. Fortunately I learned to walk and button my own shirt again, though it took a long time. That is a correlation: there is no causal link there. It's a coincidence. But even if Bill himself had stuck me with a needle full of microchips, writing it up would have zero impact.
There are lots of examples of ordinary people doing extraordinary things, and their legends deserve to be lovingly retold to generations of children. But the enormous difference they make has high costs and no rewards. If we're not professionals like my friend the bomb expert, who spent each day ferreting out killers, we're left with only one purpose for writing hypothetical conspiracies involving famous people, and that's to get attention. To get a piece of that fame and fortune. Who knows, maybe get mentioned by the Twitter-in-Chief.