It's a result of the footwork and forehand approach per zeio. If one of them can get a ridiculously backhand (and the closest one so far is LJH), it is a wrap. Lee Sangsu doesn't feel comfortable with his backhand and he has gotten pretty far.
Gotta have the live scoring on. The crowd noise watching Table 2 also let you know exactly how the match was going. If they cheered, you knew LJH was doing well.
Both are young and evolving players - winning is less important than growing. Harimoto learned a lot from this WCT match and I am sure he felt he would lose the match. He has to counter topspin more on the forehand and block less.
Who are they training with and who are they competing against? That answers 95% of your question. But seriously, no one who is 16 was more consistent than Harimoto. FZD, ML and XX were not at this level at this age.
Gewo sponsors the Nigerian team so it seems the head of Nigerian TT was able to use that to get Aruna a deal with Gewo.
https://www.pressreader.com/nigeria/thisday/20190701/282033328743526