Mo Zhao might not be as cunning or as smart as Di Fuyi, but he was undoubtedly crueler than him. As the saying goes, "the strongest person is the one with no desires." Basically, the one who had nothing to lose.
Even though Mo Zhao looked gentle, he was ruthless. No one could threaten him. He would abandon his companions if it helped him to achieve his goals.
Di Fuyi used to be like this too. However, it was now his weakness. As soon as his weakness was revealed, he was vulnerable to his enemies. Perhaps his biggest mistake was to fall in love with Gu Xijiu.
Long Fan had always treated the rules of the world like sh*t. He always felt that those rules were hypocritical and it was the reason why he would instead befriend the devil.