It relies on native libraries like libjwgl so it does still have portability issues.

And most game consoles can’t run Java so they had to totally rewrite it there.

Most game consoles are amd64 or ARM. Running java there is trivial.

Minecraft for 3DS, Xbox 360, etc already exists and is a rewrite in C++. It’s older than current game consoles.

But they don’t have JREs even if they have the right kind of CPU in them.