I mean GeForce Now is still going and PS+ streaming is surprisingly playable.

I think people just didn't want Google.

Google stupidly positioned their service as if it was a separate console you had to buy games for, which then couldn’t be played anywhere else. The successful streaming services sell you games for non-streaming platforms and then just allow you to stream them as an option.

I think the reasons are a little more boring, that it was a combination of different reasons that contributed to Stadia’s failure.