Are you kidding? This is the East Aldenard Trading Company we're talking about. You know... the trading company that was trying to bargain with Garlemald back in 1.0? The trading company that is already getting around Kugane's tariffs by dealing directly with the Confederacy? The company that blatantly says it could care less about the Sultana dying if it was good for business? An uninhabited island pops up in the Glass Ocean that no one's claimed yet? Yeah they're going to go for it.

And then there's Rowena who basically runs her own trading empire out of Mor Dhona... No matter how sketchy some of stuff she does is, everyone agrees her business sense is second-to-none and her products are legit. She will provide what people pay her for.

Like it or not, the Eorzean Alliance doesn't have a lot of control over the "frontier" parts of Aldenard. Mor Dhona is almost treated like it's own city-state (run by Rowena) as is Iddlyshire. And the Alliance has been shown to not have a lot of control over what it's larger Companies do either. It's not like Rowena or the EATC took over an island that belonged to Hingashi previously.

On the other side, this is Hingashi. They've all but let the Confederacy take charge of all the shipping in the Ruby Sea for as long as everyone can remember. Rowena and EATC are basically functioning like the Confederacy is, only instead of being between Hingashi and Doma, they're between Hingashi and Eorzea.