Deeplearning4j [1] has won deep learning on the JVM. Nothing else comes close. (Disclosure: I'm one of its creators.) DL4J has the most sophisticated Spark integration, plugs into Kafka and works as a Hadoop job. It does all that while running on distributed GPUs, multiple CPUs and heterogenous hardware. It wraps cuDNN, which is faster than Tensorflow.
Finally, part of our stack, JavaCPP [2], is used by the TF communities as well as other big company projects to bridge the gap between Java and C++.
Dev mindshare in the form of Github stars doesn't equal revenue.
Finally, there are a number of strategic problems companies face when adopting a Google project. First, they are leery of depending on Google when they also compete with it. This is particularly true because Google doesn't open source a lot of its best work, like code from DeepMind. So Tensorflow adopters are getting the leftovers in a way, and they're kneecapped in the AI race.
Secondly, Tensorflow is not platform neutral. It's optimized for TPUs, which are not publicly available. It's a play to attract people to the Google Cloud.
[0] http://keras.io/ [1] http://deeplearning4j.org/ [2] https://github.com/bytedeco/javacpp