1. Well, they dug too deep and let the troggs out. Then they nuked the place 2. You know when Varimathas said that "A Natherzium cannont kill another one"? It just might have been that that was true, as in it is physichally impossible for a Natherzium to kill another one. At that, Varimathas is a sly creature who is probably working against Sylvannus anyway, so he could have just made it look like he killed Balnazzar when infact he didn't
Nah, they irridated the joint to try and kill the troggs. It didn't work
3. Random. Ignore it 4. Its being rebuilt. That's about it 5. Because Blizzard wanted a PvP system. As in, there is no reason why they have gone to war and should probably be at a sort of peace, like in the RPG