This was in the works for years with the launch always shelved for fear of antagonizing Google and the big kahunas. It is not easy to beat the PlayStore & iStore duopoly of app marketplace. Many companies can build OS, building the ecosystem is difficult. Basically Huawei needs to get enough leverage to host developer conferences... which needs OS and such. Sanctions is only a symptom of the problem. Use the window to remove the tumor. It will be painful unless Xi order all Chinese developers to dump Android for Harmony or is it Hong Meng.
Facebook has been toying with the OS idea for years but the risk vs gain doesn't add up. Cause Facebook apps need Android and iOS. Any threat and they kill FB.