Xadem is the most responsible imo. Banning him made Luna lose all the support she had left. He made her have the decisive crack.
Causality-wise though none of that would have happened if not for TPG beating Luna in The Senate.
The fuck? That was months before, during which Luna was stable.
She banned TPG for beating her in the senate, then temporarily shut it down.
Later, the Senate was reinstated, and Xadem went on a campaign to find ways to worm TPG into his rightful seat, and she kept disregarding everything as "Troll Bills", even the little stuff.
She then went over to the Nasomi forums to bitch about them, which was then copy/pasted back onto SC so people could see how she really feels about them.
Shortly after that Luna removed Xadem's rep, then he began protesting how The Senate gets nothing done, Tryp followed suit as another Senate member and was also docked Rep over it. This on normal users would have meant nothing, but docking Senate users of their rep when rep is what weighs the votes shows a direct expression of power that entirely undermines the process she was once so excited over.
It was after this that Xadem's quiet complaints eventually got him banned.
Sure a lot of this is Xadem pulling the weight, but TPG was his banner, and without TPG's contributions there wouldn't have been a tangent point for Xadem to run his meek campaign of point-proving that ultimately spurred others into responding.
So yes, causality-wise, TPG is the prior domino in the chain of events, and a lot of that domino's weight was based on prior investment and buildup. The senate didn't add up to anything for the website, but it did contribute notably to Luna's breakdown. She was not stable at this time, and tried to run away towards a Final Fantasy XI clone to compensate (and ultimately fail when they hated White Mages).
