Wait a minute.
I didn't know Thrawn was responsible for the Ssi-ruuk's fall in 4ABY.
«Thrawn returned to his Hand of Thrawn base. He and his followers decimated the Ssi-ruuvi Imperium and established bulwarks against other, more dire threats.» The New Essential Guide to Characters (2002)
«After the Battle of Endor, Thrawn's forces clash with the Ssi-ruuvi Imperium, allowing the CEDF to invade Ssi-ruuk territory once the reptilians strike back against Ascendancy worlds. Their short war leaves the Ssi-ruuk crippled and the Chiss the de facto law-and-order power in the Unknown Regions.» The Unknown Regions sourcebook (2010)
But of course he was. Whatever bedlam’s going on in the Unknown Regions he must be involved somehow 🤷
Also, tricking the Ssi-ruuk into attacking the Ascendancy so that the Chiss can lay waste of their Imperium? That's such a simple move it's genius.
«It was quite a surprise, then, when the Sibwarra arrived at the Ssi-ruuvi star cluster and found a half beaten foe. The Chiss, striking from deep in the Unknown Regions had already attacked the Ssi-ruuvi Imperium on the opposite front. It is believed that Grand Admiral Thrawn (...) had orchestrated the attack combining his Imperial warships with renegade chiss crafts in what he was already calling his "Empire of the Hand".» The New Essential Chronology (2000)