Recovered records indicate that remnants of Family Tharka were still alive this deep into the system when the Gates started to malfunction. They had made their way towards the inhabitable planet and, even though Patriarch Tharka never managed to regroup with the vanguard expedition, they were able to sustain themselves well enough to scrape by. Presumably, the Split colonists were exhausted from the long journey and spread thinly when they encountered the Xenon. Salvaged wreckage suggests that they sent scouts to make their way back towards the Jump Gates, but none ever made it. Their mission was doomed to fail anyway, for even if they had reached the gates in time, they would have found them disconnected.
After the Gates resumed functioning, other Split families claimed the system for themselves, and soon realised that the Family Tharka line had come to a violent end. In desperation the Patriarch had overreached and, spread so thinly, they were not able to put up an honourable fight, but rather vanished without fanfare.
The Xenon in this sector are the weakest in the game, they lack both their necessary resources for survival as well as the production facilities to replenish their numbers. Simple attrition of the lone Xenon fleet based here can easily make this sector a base for the player or the Free Families.