None of those companies have a tiny little bit of interest of helping their competitors with joint development. I guess you're too young to remember the balkanization of Symbian among such companies?

Those are companies, their only interest is to maximise profit. Apparently right now the most profitable is to pay Google for the Android licence.

Huawei found themselves on their own because of the ban, and decided to go for HarmonyOS NEXT. Probably they wouldn't come back to a "joint development AOSP" now.

Now if Google lost Android, what would happen for the others? Would they each try their luck with their own OS or would they try to go for a joint development?