As proven in several cases, it is mostly caused by management not willing to keep the required investment to make it happen.

Projects like Midori, Swift, Android, MaximeVM, GraalVM, only happen when someone high enough is willing to keep it going until it takes off.

When they fail, usually it is because management backing felt through, not because there wasn't a way to sort out whatever was the cause.

Even Java had enough backing from Sun, IBM, Oracle and BEA during its early uncertainty days outside being a language for applets, until it actually took off on server and mobile phones.

If Valhala never makes it, it is because Oracle gave up funding the team after all these years, or it is impossible and it was a waste of money?