How did the TImelords get wiped out?
I just got a chance to see the second episode, and now I finally understand why you asked this question.
I've no idea. When the Doctor broadcast his last episode years ago, there were still plenty of Timelords and they seemed like one of the ultimate powers in the universe. (Hamstrung by an overactive sense of restraint.)
Now this new 2005 Timelord says there was a war and they were all wiped out, and he's the last one left. So far as I know there is no information (yet) on how this happened or who did it.
Frankly, I'm a little sad. I enjoyed the Gallifrey episodes. And I really enjoyed The Master; especially as played by Roger Delgado. If The Doctor is the last Timelord left alive, I guess The Master is dead too.
Now that's just not right.
-S'Cipio