As you know, Sam has the telekinesis technique, and he also upgraded that technique to C-grade. So you can say that it is also one of his powerful techniques. But because he did not usually use that technique, nobody knows that he has a C-grade telekinesis technique. Everyone only knows that he has a low-grade telekinesis technique.
Now, coming back was the main matter. While Sam looked towards the audience leaving the stadium, he suddenly felt a mental energy fluctuation. When someone uses mental techniques like mind control techniques or something like that, they convert their spiritual energy to mental energy, and only then are they able to use that technique. Also, he did not feel any low mental energy and because of this, he suddenly became very startled. Who was using the mental energy and for what purpose they were using that technique?