TensorFlow (and stacks built over it) has the greatest mindshare, which allows Google to both optimize the capabilities of its ML offerings based on TensorFlow, knowing most developers will be familiar with it, and to increase profit margins on those services at the same time. TensorFlow makes a significant part of the ML stack convenient and accessible, and releasing it for free opened the flood gates for Google to expand the machine learning industry significantly while shifting the profit generation away from software and onto the cloud (data storage + compute resources).

Sublime execution, really. Once machine learning passes through this hype cycle (over the "trough of disillusionment" and onto the "plateau of productivity"), Google will likely have made the majority of the machine learning industry accessible enough for most software engineers to pick up something like TensorFlow and hit the ground running, which will gradually exert a downward pressure on ML specialized salaries for all but the top end. But this will continue even as the industry continues to expand, which means Google will come out ahead earning even more profit even if salaries plateau or decrease.