Some consider Keras to have an easier API than TensorFlow.
Also I see evidence that Keras Developers work with TensorFlow developers.
I list a blog post below:
Buried in a Reddit comment, Francois Chollet, author of Keras and AI researcher at Google, made an exciting announcement: Keras will be the first high-level library added to core TensorFlow at Google, which will effectively make it TensorFlow’s default API. This is excellent news for a number of reasons!
As background, Keras is a high-level Python neural networks library that runs on top of either TensorFlow or Theano. There are other high level Python neural networks libraries that can be used on top of TensorFlow, such as TF-Slim, although these are less developed and not part of core TensorFlow.