to phrase it as a jerk, l2dr
or nicely: (s)he was still under the effects of "diminished returns" (henceforth dr). every attack on a country beyond the 2rd in a 24 hour period reduces the gains of future grabs on that country. every successful (could be wrong here, but I think that's somewhere in the changes) attack made by the country removes 1 from dr level (ghost dr remains for 24 hours no matter what, but that's a seperate topic). check their full news from the last 24 hours and you'll see there was still dr on the country when you made your grab.
for easier checking (and just plain better formatting than ingame news) try
http://www.earthgraphs.com or
http://www.eestats.com