Ah yes that's true, I always seem to group .io in with the new crowd of TLDs in the sense that it became trendy "recently"; and I only mentioned .io domains since GitBook uses one, "gitbook.io".
.io isn't just "Indian Ocean", it is British Indian Ocean Territory. The location of the Diego Garcia military base (jointly operated by US and UK). The British expelled its indigenous population (the Chagossians) to make way for the US military. The territory is claimed by Mauritius, and the International Court of Justice in 2019 ruled (in a non-binding opinion) that the UKs separation of the territory from Mauritius was unlawful.
Some random British company convinced IANA to let it run the .io domain for their own profit. Their operation of it has nothing to do with the interests of its exiled inhabitants (the Chagossians), the British territorial and military authorities, or the US military presence which constitutes the the territory's raison d'etre.
I think it likely that, one of these days, something is going to happen to the .IO ccTLD operators. Their rights to it are very dubious, and someone else (the British government, the government of Mauritius, the Chagossians) could end up wresting it from them.