Conspiracy theories are so unbelievable that you can easily make up a more believable one yourself. Here's how.
Disclosure: This is a thought experiment for the purposes of showing how easy it is to make up a conspiracy theory. I do not advocate the dissemination of conspiracy theories and other baseless speculations.
Do some of the conspiracy theories out there seem so far-fetched that you are ROTFL when you hear of them? Yet some people actually do seem to believe them. Many conspiracy theories are made up. In other words they are fiction. At best, they are theories and not fact, otherwise that particular conspiracy theory wouldn't be a conspiracy theory, it would be fact. At worse, they are the deliberate peddling of lies.
So I decided to demonstrate that creating a conspiracy theory is so easy that anyone can do it. There are no special skills, talents, or level of intelligence required. There is nothing special about making up a conspiracy theory. Let's have a go.
Step 1: Identify the least believable conspiracy theory you have heard of
This step is easy and should take you less than a minute. The good news for you here is that conspiracy theories set the bar is so low in terms of believability, that you should have no problem finding a not-very-believable conspiracy theory that exists.
It doesn't matter how many or how few other people happen to believe in it; it just has to sound ridiculously unbelievable to you.
Step 2: Make up your own conspiracy theory that is more believable than the one in step 1
By this, I mean that you need not actually believe your own conspiracy theory. Likewise it does not need to hold up to journalistic scrutiny or fact-based evidence (the one in step 1 likely doesn't). Yours also does not need to sound believable to anyone else, it just has to sound more believable to you personally than the one in step 1.
So you're trying to create something that, even though you don't believe it, sounds like it makes marginally more sense than the one in step 1. In case you can't think of anything at this moment, don't worry - there are conspiracy theory generators online you can use. Try the conspiracy theory generator at Chaotic Shiny or the conspiracy theory generator at Generator Fun.
Step 3. Done
At this point, using either your own brain or technology tools that are available online to anyone, you have managed to come up with one or more conspiracy theories that sounds more believable to you than the least believable one you have heard of. Yes, it is really that easy.
As you can see, there are an almost infinite number of conspiracy theories you can generate, creating variations upon variations of them. They would be pure fiction, but they are easy to create.
So if it's that easy, why do people actually believe some of the existing conspiracy theories?
Now we come to an intersection of technology and a bunch of other fields, none of which I am expert in. It's not just the supply end of conspiracy theories that we need to look at, it's the demand end too.
In other words, given how easy we saw it was to just make stuff up, why does anyone ever believe an existing conspiracy theory in the absence of hard journalistic-level evidence? Why is their reaction to believe it in the absence of a journalistic level of evidence?
This, by the way, is the same question as "Why do people buy tabloid newspapers when they likely know that much of it could be libel or slander?"
The dissemination of lies would quickly die out if there was no demand. Yet there is clearly demand.
I think that the answer is, there are people out there who value fake answers to questions more than they value the truth.
To paint it with a finer brush, there are people who, when observing a complex situation, would prefer to believe a made-up theory than to wait for evidence. They are impatient to close the question, and would rather have it closed with a straight-out lie, as opposed to leaving the question open and waiting for evidence.