Although a Three-Headed Cerberus was known for having three heads, the real decision making part of it was always the main, middle head. The other two were actually something born from the main head, and was part of a single whole.
It was similar to replicating the consciousness of the main head, and like a person with schizophrenia—each head could possess different personalities, but there was always one main persona in control.
However, the situation right now was completely different! Each head already had a complete set of memories and individuality. In a sense, every single head was the main head!
At the same time, the main head's own mental power was being split into three and given to the other two dunces, unlocking their intelligence!