A major difference though is that Broadcast TV (or cable TV, or Satellite TV, or Youtube) only has to attempt compression on an individual stream once. If 500 or 50000 people decide to watch that item, it still only needs to be compressed once.
In the case of almost ALL content other than Live Broadcast Events, all of that compression work gets done well in advance of broadcast, and with Live stream events, there is usually a several second delay, which allows the Compression Codecs at least a small chance to get some work done.
Stadia is going to be thousands upon thousands of 100% unique streams, all requiring as close to real time compression as possible (time delay like you get in Live TV broadcasts would be completely impossible because you can't offset the broadcast by a few seconds to allow the encoders to work if your source is also receiving continuous dynamic input like from a game controller). It's literally orders of magnitude more difficult than simply streaming a Youtube video or watching your latest episode of Game of Thrones.