Oh yeah, because when the Northern Alliance was trying to sack Barad Falas Eston was in major danger of "losing everything." What the heck, man?
Well, sorry. The only logical way to explain your move is that you wanted to reduce your battlefront and be covered for if this war failed. And maybe you wanted to piss of/copy darka for having a treaty with Talerium but you know, none of that is very risky.
Of course maybe none of these motives played in your decision but then I wonder which ones did..