I'm aware. This time, SteamOS is much more mature and consumers are primed for such a move. Especially if it's more tightly controlled by Valve instead of allowing 3rd parties more leeway.
Those were capable of nothing but streaming games(didn't even have a native web browser). Why would it be comparable at all to a machine that runs games locally?
You are mistaking the Steam Link hardware with Steam Machines which were real computers made by several 3rd party vendors (Alienware, Asus, Gigabyte etc.)