It was in a mostly stagnant state, a release once in a while, and now it's going regular and strong.
The thing is, after things get the "CNCF" stamp they kinda go viral and become the "de facto" standard.
This means that Harbor would become the most usual way to run a private registry and thus Quay would lose ground (=> harder to sell).
Source: just implemented Harbor at work. Quay would probably have been better (probably "production ready") but Harbor was free & open source.
