It's weird seeing comments like this in HN. The "proven" approach is just a less controversial way of lighting money on fire.

Google wasn't going "all in" on "unproven" technology. They were making a strategic investment in a new market segment using technologies and people that it already was an expert in rather than trying to follow the footsteps of competitors that have several decades lead on them. And they're not betting the bank on stadia. They could turn it off tomorrow and it wouldn't make a blip of difference to the health of the company.