The simple fact is that computers vastly outcompete human chess players. And not just big and expensive purpose built machines but the kind of computers everyone has access to.
Furthermore at the skill levels these players are you don’t even need constant handholding from a computer. A few hints at key moments would be enough to basically shift the balance in someones favour.
So if someone wants to cheat all they have to do is to receive a few bits of information from an accomplice. The question is not even if someone cheated in that particular game, but if cheating is possible.
We can imagine all kind of spy gadgetry one could use to communicate those few bits. People have two hangups with many of them: they can be found in a security screening, or they sound too sci-fy.
The vibrating anal beads combine three properties: - they could transfer the few bits of information needed to tilt the game in favour of a cheat. - they are not too far fetched. You can buy them right now commercially. - they would be very hard to detect by security arrangements. It feels very unlikely that players would agree to the kind of invasive probing which would be necessary to detect one.
So it is not that people think that this particular player in this particular game actually used vibrating anal beads. It is more about the idea that someone could cheat at chess with covert communication methods.
The key takeaway is that if you have someone assisting you (entering the information into the computer) they only need a very simple way of sending a signal - which could be a "do something unexpected" or "this move is crucial". And you'd only need a time or two in a game to get the edge, assuming you're already skilled at the game.
1. The trope of the 'Depraved Homosexual' has a long established history in pop culture and cinema. Anal beads as the choice for cheating would fall, comfortably, into that trope. [https://tvtropes.org/pmwiki/pmwiki.php/Main/DepravedHomosexu...]
2. Chess is full of VERY smart people. One of the most common ways to insult a smart person is to call into question their sexuality; hence why we have to have entire movements related to calling out anti-lgbtq+ statements like "that's so gay". [https://welcomingschools.org/resources/stop-thats-so-gay-ant...]
Anyway, combine those two things, and you get your answer. It's because the world hasn't really evolved at all in the last 30-40 years, outside of what we have been forced to do by law. It's easy and socially acceptable to call a man gay as an insult, so in a roundabout way, that's what we're getting with the anal beads talk.
I sort of laser focused on this last week when I heard this theory for the first time. It just struck me as so. . . odd. Why would that be a thing? That's what I came up with.