When you have Google's resources and talent, you probably need a reason not to do these kinds of things. If a product has a decent chance of generating revenue or building out consumer profiles or reaching a new demographic and doesn't undermine the ads business, it has a shot of being pursued.

For gaming, I bet you could make a strong case that Google needs another hook into younger users who will stop using Google search the second their phone changes default search engines. Kind of an insurance policy.

The psychological profiles of users that could be built are also kinda terrifying. Hopefully that's not a part of the business case for Stadia.

Finally there's a case to be made for synergy with Youtube and its efforts to compete with Twitch.