The instigators-2
He waited years for any opportunity; the only problem was that he couldn't do anything in the open. With his father still at the company's helm, he had to skirt under his radar to not upset him.
He also had a younger brother trained in the family business. His brother was gifted from childhood and was considered a genius by many, which led to his father favoring him quite a bit.
If he openly sabotages a good employee's career, he would have to suffer the consequences with his father. Just as he was panicking due to the recent success of Kim's concert, one of the people under him showed him the actual stage performance.
It was the team leader of Equinox, Seo-jin, one of the top bands under him. He was Jung's one confidant that he trusted the most. His coming to him with any information meant he was particular about it.