Lol I saw this when it came out and we had another thread (or not, I might be getting DejaVu).
My pet theory for why they did it like this is:
they fired any experienced dev and told a bunch of juniors; whose experience was only in react, to write a TUI. The juniors obviously thought they would code up the backend first because they were like "TUI? What's that? Some kind of web frontend that looks like the cmd.exe?" and then it was just a terminal-like frontend rendered using a canvas.