Leeches

By leeches I mean weaker nations that feed off of strong nations that are being attacked by a bigger nation. An example would be when I was about to take down the player with the most VP in game and since everyone was scared of him no one would help me, after a long war I had taken about 1/4 of their land and most of their army was gone. About 3 nations that had refused to help me were now attacking that bigger nation, desperately trying to get any land they could before my forces swept through the remaining land. Has anyone else experienced something like this?