Jidenna was able to conclude with the numerous evidence including, the weird vibrations only he could see, the recordings and what his own eyes witnessed.
Jidenna finally concluded that, "Firstly, Cheng Yuan's abilities manipulated people and secondly,
Cheng Yuan's abilities could only affect a certain group of people based on their personality and thirdly,
Cheng Yuan's powers might have the ability to alter people's perception of himself making it favourable.
Infact it was more than just making it favourable it was more like turning the person into a loyal supporter who wouldn't dare to go left if Cheng Yuan's orders them to go right"
Of course Jidenna had to think and rethink to make sure his conclusion was spot on and even thought it wasn't at least it should be very close.