Java was an incredibly popular language in 2001. I had been using it in commercial apps for four years. It was around 2001 that I was managing a development team and was introduced to Python. About that time, I also began to realize how expensive Java development was and how many more interesting ideas were happening in other languages.

While it was clear Java was popular, it was also clear it was stagnating under the beurocracy and the weight of its corporate champions (small changes and backwards compatible at all costs). It also became clear that there weren't going to be many repeats of Java's initial ideas.

On the insights, I probably give Java more credit for than pg would because they pretty much all exist in lisp, but Joy packaged them for "easy" consumption. Arguably, the most important was the JVM and the notion that bits didn't need to run on the metal directly. This was well known to the lisp and smalltalk communities but shunned more generally, but Java made it acceptable across the computing ecosystem to run in a VM. This really opened doors for languages like Python and Ruby. It would be interesting to know if they would have been as popular without Java and it's corporate marketing machine telling developers VM are good.