Google would need to solve speed of light problems for Stadia to be successful. It's not that people are betting against Google, they are betting on their understanding of physics.
Stadia is going to be the luke warm product that OnLive was and then Google will shutter it. AT&T also tried to do this kind of service in limited markets with fiber optics to the home, servers near the last mile, and a partnership with nvidia for rapid decode/encode. Didn't stick. Why will Google be successful?