It seems like the incentives for employees at Google are the problem here. People are rewarded for successfully completing projects, not for maintaining existing ones, so rational employees will maximize their compensation by moving on from a project after it launches and trying to launch a new one.
There seems to be nobody at the top enforcing a consistent product vision.
This is how Android ended up having several text messaging apps at the same time a few years ago. Apple certainly would not have done that, and I doubt even Microsoft would have allowed that state of affairs to exist.
