Cha and Gogo were already exceptional skaters at their age when they got to Brian... and for what it's worth, it didn't work out for Gogo.
From the look of last season, Gogo's move isn't working out too hot either as yet. It might right itself now in the run to 2022.... or not. Which emphasises the point that there is no one size fits even 40% let alone all in elite sport nor (for all we love to do it) does second-guessing. Every coach has failures, everyone at this level has wild successes and some of them are another coach's 'duds'.
Rika is adding Brian, not moving completely from Hamada, which shows she and JSF believe they both have something to bring to her already impressive skills, and she can aim for the best of both worlds. The thing is, the Mess That Is 2020 not withstanding, these days it is a lot easier to move internationally, both to a new coach and back and forward to co-coaches, so the highly ambitious will probably and increasingly take advantage.