Just to make everyone clar on this:
DOTA has basicly 2 endings - one victorious and one that ends in disaster.
The two endings you see on the graph are the same, but from a different angle (that endings are last missions if you fly normal military OR SOC).
In other words, the story is the same, the ending is the same, but you can come to it trough either the SOC tree, or the normal military tree - note that the last missions are different, but both are of utmost importance for the final sucess.
And they are conectedd...for instance in normal tree the player must hold off a large Shivan force, while in the SOC campaign one must attack a large Shivan base. So, in the normal campaign 2 Shivan warships jump in and manage to ecape trough a jump node. A minute later you hear a transmission from the SOC forces that those ships are attacking them.
If you play SOC, you'll hear a transmission that 2 shivan warships have escaped, and a minute later they'll jump in and attack!
If the pilot fails in any of these missions, then you have a disaster ending, otherwise a victory ending.