What exactly does DeepMind even do that provides investor ROI? I can't call it a good acquisition.

Deepmind Health was a pure-data play, like most Google acquisitions; including Fitbit ─ which might initially suggest it is a way to sell gadgets or a platform but reverse is true ie. it is a strategy albeit not a cohesive one, to acquihire and/or gain foothold in a sector, especially where it does not have a dominant presence, in order to integrate a disparate portfolio of existing services.

https://deepmind.com/blog/announcements/deepmind-health-join...