Because you listed several positions. As someone else mentioned, he's a good or maybe very good HS RB (hard to tell from highlights the level of competition) but he didn't have the kind of moves you'd expect at D1 (look at his lateral moves, which worked in these highlights but would never work consistently at D1).

That said, TCU tunred into a very good D1 team by recruiting RBs and cinverting them to other positions. No idea of this guys frame, size,'or defensive instinct. But that may be the route for him.