The purebloods thought they would teach him politics. Greengrass already had plans to do a spiel on potential and being grey. However, Harry just himbos everyone into loving him, and some into becoming obsessively devout to him(the true trait Syltherin looks for is acually willingness to obess about things and or become devout to a person/cause). Which tbh is very canonical Syltherin.

Anyway, soon a cult forms around protecting Harry, doing his will. Snape starts having to treat Harry better as he becomes legitimately concerned for his own safety. A suspicious amount of parents of death eaters die in "accidents" when their kids come home for the holidays.

Can be played straight with Harry not understanding what is going on or him being very aware and actively running his cult.