First, this came during the whole scare about daemon invasion. The actual war being declared came shortly after Netherworld declared war on everyone. Really, not a great time to go deciding you want to just go on a land grab.
This was in progress before the Netherworld showed up, and it will probably be a very (boring) long time before LE or Summerdale are anything other than cheerleaders in any war with Netherworld, so why wait on that?
Second -- and this is the part that makes it really funny -- they have less nobles than regions already. And they are basically saying 'we want more regions.
You're reading it... the way you want to. When I read the declaration, I think "Both realms are successors to Springdale... there should be only one!"
Either way, some fun in the north again!