The reason was quite simple actually, Tianlong Yun knew about their presence because he was the one who had planted the seeds.
He was clear, more than anybody, that the human mind is fickle, and that you can never truly control it, and there are many two-faced, or multi-faced people amidst them.
No matter how perfect or how ideal something looked on the first view, no matter how good the selection process was, there were bound to be some bad apples mixed with the good ones.
If he left these bad apples work out of his sight, no matter how weak and insignificant they were at the moment, he was sure that they would cause trouble when they shouldn't for him.
They were a dangerous factor that he couldn't leave alone, so he had thought of the best way to deal with them.
Since they were bound to spring out, he decided to plant the seeds for them, he gave them 'friends' of the same cause, like them, he gave them a 'place' where they could belong.
