Could be any number of reasons really. There's been a number of DDoS attacks against the game servers in the last year or two. Could be a group hoping for a payday from SE to stop the attacks. Could be a bunch of bored script kiddies who like the fact it gets media attention. Could be SE's still got some bad net code in the held together with duct tape engine FFXIV runs on and it's actually caused by the players 😂

Regardless, we likely won't know the specifics of what's happening as that will be kept private by the game's security team. If they feel it was bad enough we might get an apology from Yoshi-P and some free days but probably not at the moment if I were to hazard a guess. It's not day 1 savage or anything like that.