A lot of explanations, the ending of the Exile his companions. Atton the Disciple/Handmaiden, Mira or Hanharr they shoudl have all died.
HK factory was completely removed. The reason why G0-T0 is on Malachor, normally you are supposed to find out he build the HK-50's of course you don't. There are some topics about this on several forums, I would recommend you just search for them they can explain everything in far greater detail then I can.