Why most of the Apache projects use Java/JVM

Java is a very strong programming language in corporate environments. A few years ago nobody would suggest using rust, or even golang. These languages were too young. Java is much safer than c++ and much cheaper to maintain.

Also the performances overhead of the JVM is not a problem at all for big data, since you can scale horizontally and cloud cost isn't really an issue. Having good c++ developers and having a high quality code base in c++ over the years is more expensive.

I don't like Java that much and I play more in golang and rust these days. If I had to decide which programming language to use for a large company for very long term project, I would answer Java without any doubt. Or C#.