Years ago, the visiting Elementals representatives made their first contact with the alliance.
When the alliance realized that they came from a unique galaxy that was filled with beings like them, their first thought was obviously forcefully conquering it.
Unfortunately, all of their people went missing and a connection to the UVR wasn't established...So their excitement washed away from the fear of the unknown.
This pushed the alliance to engage with the visiting Elementals representatives in a civil manner.
Through their discussions, they found out that their galaxy would remain inaccessible to outsiders and even reject the establishment of the network there.
Even though those terms were too hard to swallow for the ten rulers, they still agreed to have them join their alliance.