Simply spoken: because I know it the best.
Being a developer profession-wise I worked the past 10 years with Java. Usually on much higher level than with this project though.
When I started out, I was not aware of what is lurking in the dark. And I was not expecting that there would be so much effort to solve small issues. Honestly, if I had started this with a new programming language, I'd probably be stuck after some months because I wouldn't have a clue how to get move on.
About...