TensorFlow was honestly not that good. It had a lot of effort put into it, so it worked, but there are reasons people moved away from it.
I think Jeff Dean is a great engineer, but I wouldn't hold up TensorFlow as a great example.
I always thought he pair programmed so it's been Jeff + Sanjay.
Why wasn’t tensorflow good?
I started my ML journey in TensorFlow, and now I am a happy PyTorch user, for many years.
TensorFlow, yuck
But who uses TensorFlow -- really -- these days.
What else are people using then?
PyTorch everywhere
Or JAX
Google does almost exclusively; it's tied in to TFX.
Of course he is someone any technology organisation would want to have as a resource. But probably not as chief scientist or ceo of an ML company based on the available evidence