They sort of did:
Huawei has apparently been developing a secret mobile OS for six years
I think their OS, if it does go mainstream, will be for mainland China users only.
Before they decide to use it and go up against Google and Apple, they should take a page out of another piece of tech history.... Microsoft, in all their might, hardly made a dent in the mobile market share with their Windows Mobile OS running on Nokia hardware, which caused them to give up on it and went to partner with Google/Android instead.