The thing about conspiracy theories, is that some of them are right, at least in part, the problem is the people that are most inclined to believe them are usually incapable of applying facts and logic to the theory, especially if it’s a juicy one.
They let their hearts rule their heads too readily, because they so want it to be true, principally for reasons of self-vindication.
Too many people would need to be in on this to make it remotely plausible.
The PEDs thing, maybe I guess, but the notion that there was a widespread conspiracy to make Leicester win the league that year from before a ball was kicked descends into the realms of the absurd.