Consider that this effort started 20 years ago, and also consider that if you want to hire a general backend developer today for a reasonable price, Java is the language to pick.
Java is the safest bet if you want to write something that will be maintainable at reasonable cost through the next 50 years.
Oracle (i.e. Java) & "reasonable cost" is a surprising pairing.
Java licencing is manageable compared to the cost of developing a human resurrection technology in 2100 to bring back to life developers of by then long-forgotten technologies, which were hip in 2020. I bet Java will still be doing fine in 2100. Furthermore, the support of a behemoth such as Oracle is very reassuring for large businesses, which know that they won't be left alone with their tech stack. Can the same thing be said about Python or Scala?
Hinted at this before but what makes you think Java will be around in 2100 or even be in a form similar to that of today.
There's an unimaginable amount of business critical code written in Java already. Java is seen by businesses as good enough, so, barring some breakthroughs in CS, there will not be much pressure to migrate off it. And even if there were (let's say Oracle starts charging unreasonably much for Java, the way IBM does for mainframes), we can still see plenty of COBOL/MF architectures in the wild today.
Given that they're rewriting something that was 40 years old 20 years ago tells me that it might be an impossible task given the current attitude of software development as a whole.
They decided on Java and .NET because they needed to hire contractors in DC that had those skills.