Microsoft is hedging, because they're behind the two leaders (Sony, then Nintendo. Lets not get ahead of ourselves here). Whether they're genuine or have ulterior motives is irrelevant, but you should watch some of Phil Spencer's interviews; it feels very genuine.
Stadia's business model is identical to every other game platform's business model; percent of sale. So, to be clear about this; you're suggesting that Stadia can support a global DC footprint with massively expensive silicon and networking, off of the same revenue stream that Xbox, Sony, Nintendo, Valve, EA Origin, etc all already utilize, these companies who don't have infrastructure investments of the same magnitude or clearly plan to have a more distinct subscription category to support it? The economics don't make sense. They have options: sell ads, get rid of the free tier, create a pay-as-you-go paid tier based on time played, shut down, etc; but none of these look like the Stadia people are excited about today.
Microsoft also has first party titles. They own some of the strongest IPs in the history of gaming (Halo, Gears, Forza, Minecraft). They have the most powerful consoles. They run sales all the time. Doesn't matter; the X1 was the poorest performing console this generation.
Creating new gaming studios is difficult. Creating games is difficult. Creating great games consistently is a feat only a half-dozen studios in the world have figured out. Games that sell consoles generally come from creative teams with VAST cohesive industry and technical experience, not from new studios.
Halo 1, 2, and 3 were fantastic; then, Microsoft formed 343 Industries to build Halo 4 and 5, threw a billion dollars at them, and they were a shadow of the former games. Stardew Valley was made by ONE GUY with no money, and some estimates put his revenue between $50-$100M. Anthem was made by an insanely experienced studio (Bioware) with massive amounts of cash, a deadline 6 years out, and a proven history of successful titles; it sucks. God of War (2018) was made by an insanely experienced studio (Santa Monica Studio), with massive amounts of cash, a deadline 6 years out, and a proven history of successful titles, and it is widely considered among the best games released in the past decade.
There's no pattern to why a game will be successful. Its not about manpower, or money, or talent, or anything. Stadia Game Studios probably won't make anything capable of driving meaningful revenue in the next 5 years. Maybe they'll get lucky. They probably won't.