Let me go down the list whodunnit style:
Zepla, MTQ, Stal, etc (TRUE AND HONEST WAHMEN):
Near 0% chance. Women only really look at leaking information as a potential status gain if it's information that's about or could affect interpersonal relationships. They'll leak stuff to destroy another person's life but probably won't leak class details for clout among raiders (especially since they're already high-status in that group). Only way it'd be one of them is if they were angling to pin it on someone else and get them excommunicated from the community. But still highly unlikely.
MrBrappy
This guy is as close to an 'official mouthpiece' content creator as they come. He corresponds with yoshi-p semi-regularly and has probably been trusted with prerelease information long before the media tour was even a thing. As he's never leaked anything in the past and is apparently a tight-ass even to people he's close to, I highly doubt it's him. The only way it might possibly happen is if he started working on his vids early and handed off the footage to an unscrupulous editor or something. The goodest of goodboi FFXIV creators to the point where he'd probably get a pass from yoshi-p himself even if he did turn out to be the leaker. About as likely as the wahmen.
Larryzaur
Took an extended break from content creation around the release of Shadowbringers because he had a child. Has dipped his toes into other games so his brand isn't as tightly bound to FF14. I still consider it unlikely because he's very explicitly a casual raider and prefers the less tightly-tuned stuff like Eureka and hunts etc. Like with Happ, he might unintentionally be the leaker via an unscrupulous editor but as far as I know it's just him and his wife who work on the vids. Unless his wife is ambling to ruin him or something, I don't think Larry is the leaker.
Meoni, Desperius, Ilya (third-string youtube content creators)
All have recent drama that would make them consider nuking relations with the community as a possible option. All are Euros and therefore highly duplicitous (especially Meoni, the eternal anglo). Still not very likely since these guys don't like to do 'speculation' content and instead focus on things that are already in the game.
Xenos and Arthars
Whiny raidloggers but also not very cliquish. Both of them regularly jump around data centers for different raid scenes and raid with randos from their chats, so they don't really have a coterie of raidtroons to impress. Neither are on the media tour so they'd have to have swiped the footage from someone on it. Can't see it tbh.
sfia
Has his hands in many pies and despite not being on the media tour, could probably browbeat someone who is into sharing deets with him. Apparently has a strained relationship with the other members of TpS and has been struggling to fix that. Motive and possible means, but also he's retarded and busy farming clout in other ways.
Suspect #1: Rin
Simpering soy-filled beta male who reminds me of Taliesin. Desperate for Twitter clout and for approval from other raiders. Has a bad habit of running his mouth and then having to walk things back. I don't know who let him on the media tour, but they need to be fired. Highly likely.
Suspect #2: Asmongold
Unstable NEET goblin who has fuck you money and might resent the spotlight being on him during such a tumultuous time in his life. Has been known to self-sabotage in the past. Also really bad streamdeck discipline and has streamed gameplay footage without realizing it in the past. I don't think it's him personally because I think Rich and the rest of the OTK guys would have come out with a PR statement the second the leaks became public to try and soften the blow (and also throw Asmon under the bus). He has done some insane shit in the past though, so who fucking knows.
Suspect #3: WAITO PIGGU GO HOME
The schizo theory. A certain segment of the JP playerbase has always resented the amount of attention SE pays to the foreign fans and a crazed netouyo could conceivably use these leaks to smear foreign players as untrustworthy and push SE to interact less with them. 天皇陛下万歳 ! ! !
