Getting a high adoption OSS project takes more than putting a repo on GitHub. In some cases like this one, it’s possible that the underlying cost of these activities is much closer to the licensed proprietary software than the OSS variant (aka free)
Why? Open source projects are released with "NO WARRANTY", which includes the possibility of dropping maintenance at any time. If you want continued support you either fork the project and DIY, or pay someone to support you.
This isn’t like a software company taking over some abandonware tool that they rely on. Building and maintaining software is not in the wheelhouse of these companies. They’d rather spend more or have fewer features in exchange for lowering risk.
Are you saying that it would be unethical if Google find out they'd now rather work on something newer/better, and stop having engineers contributing to it?