The steam controller didn’t really fail, but the patent fight was a mess that took way too long (much too late disqualified patent over paddle buttons). That sucked a lot of energy out of the project. Don’t forget the steam deck kept those touch pads (although with a different design)!
Steam Link IMHO also wasn’t bad, but there didn’t seem to be much interest in it then. (interestingly enough I think it could be recreated today in a Chromecast-like form factor)
Stream machines was definitely a big mess however, there just wasn’t enough interest, too limited compatibility, the machines just wasn’t versatile enough for average Joe to pay for one.
Now you have to reread this too