>>6304
I can only assume his motives were the same as Sheev's in the EU: build a unified galaxy under the Empire that can fight off the vong. This motive is actually hinted at in Zahn's nu-canon Thrawn book on pages 388 and 389.
>"There are evil things in this galaxy, Nightswan. Far more evil than the Empire, and far more dangerous to all living beings. We know of some, while of others we have heard only rumors. We needed to know whether the Empire that was rising from the ashes of the Clone War could be an ally against them."
>"I had hoped merely to persuade the Emperor to allow me to study the Empire's political and military structure under the pretext of sharing information about distant threats. But his offer gave me the opportunity to learn much more."
These two statements make perfect sense if read in the context of the EU rather than nu-canon. The book also reveals that Thrawn's exile was simply a ploy by the ascendancy to help him get close to the Empire. Zahn is getting a second nu-canon book about Thrawn published already and he seems to enjoy using them to drop hints about EU lore between the lines.