The purpose of this treaty is simple, it gets liberty off our backs so we can focus on the real threats. We cant handle fighting on three seperate fronts at the same time with such limited numbers of ships and pilots - and right now we've got liberty, the bounty hunter's guild, and the nomads/keepers all trying to hit us simultaneously.
If we can form some sort of nuetrality agreement with liberty through the tenabras, it means that we have one less enemy to deal with for the time being, and that means we can focus an extra third of our forces on the bounty hunters and nomads.