People need a narrative. People believe in conspiracies, like they believe in deities, because they need to feel that ‘someone’ is in charge and keeping life under control. They can’t accept that strange, bizarre and terrible things just happen for no reason.
It is also curious that people mostly turn to conspiracy theories to explain failures. This tendency is another example of Confirmation Bias and Attribution Bias. Some will chalk up windfall good luck to sheer fortune and others to perhaps divine intervention. But, even in the most random events, they assert some sort of personal control (“You know I had a feeling that my lottery numbers would come up this week”). I don’t know of any instance where people contrive conspiracy theories to explain windfalls (“I bet a bunch of my friends love and admire me so much that they plotted to hank the National Lottery system to make sure that my numbers came up”).