I was super excited by the live streaming capabilities of Stadia when I was first able to use them but after a but of time with them found it is really difficult to build up a community using YouTube compared to Twitch. I do understand it is in Beta so maybe they have a plan for a section in YouTube menu for Stadia live game streaming later but now as niche as Stadia is it is just a as difficult to build a following as it is to find people in multiplayer games.
Furthermore, the official sub reddit does not allow Stadia live streamers to promote their streams (just as they don't allow LFG posts in a community that desperately needs it). Instead, we have a sub reddit filled with controller pictures (some with pets), game screenshots, and requests to port old games. None of which supporting the fledgling streaming or multiplayer community which needs the most help right now. This position is a mistake in my opinion and they are strangling their own loyal fan base.
I hope rather than just going out and spending tons of money to promote their services through established streamers they start engaging their own indigenous streaming community and provide some support. Perhaps make a post on social media asking for Stadia live Streamers to post their streams to create buzz. Lift the ban on Stadia live stream promotion in the rather large official sub reddit community. Last but not least, create a category of YouTube specifically for Stadia live streams. Help your community grow so they can better help promote your brand.