Fang Zhou was being the good guy and doing good deeds non-stop at first.
But as time went on, he felt something was amiss.
After all, he wasn't truly there to participate in the entry-level trial, so why was he working so hard? And what if, by mistake, he outdid Xia Wenqiu and Ji Congfeng?
After all, he is now unaffected by the illusion, and could easily disguise himself as a paragon of justice with impeccable character.
Nobody's perfect, and the other Trialists within the illusion would definitely reveal some issues more or less, unless they could, like Fang Zhou, remain unaffected.
On this point, Fang Zhou had already beaten everyone, competing with others like he was playing with cheats—if you're working this hard even with cheats, should the others even bother to live?
So Fang Zhou started to slack off, not being as active in his good deeds; just going through the motions was enough.