In the process of a clan's growth and expansion, the number of offended enemies and potential enemies they accumulate is certainly countless. Otherwise, the clan could not possibly have grown and expanded—territory is seized from others.
But when such a number is spread out over the course of history, it doesn't seem that much anymore.
In plain language—recently, the Xue Family has only offended a finite number of people. After eliminating the unlikely ones, it's fairly easy to lock onto the suspects.
The Ji PingAn gang were the most suspicious, and only Combat Cultivators could possess such cruel and violent methods.
To give an example, exterminating an entire family is something Gu Cultivators are also adept at, but after they slaughter a family, they usually take away some of the useful items left at the scene—take the Qingback Bulls, for instance; Gu Cultivators would definitely take their corpses with them.
