When Google bought it, it felt a lot like buying the market. What Fabric tools are you going to miss, which Firebase does not have/support?
It doesn't make sense for Google to maintain two platforms that do the same thing indefinitely.
Twitter didn't have viable alternatives. They could have sold it to someone else, but who?
- Apple? Forget about Android support - Facebook? Not interested, they killed Parse - Google? Made sense, because the value of Fabric was the number of devs using it.
Fabric Crash Analytics was a strong product, why not bring in the team that developed it to gradually bring its features into Firebase?
Fabric is not a good example; it wasn't "abandoned" as developers were given alternatives. It also works better for us developers, because now I don't have to bundle a Fabric SDK and a Firebase SDK.
Lastly, given that Twitter is shutting down access to third-parties to their API, the value of Fabric's integration with Twitter might have dwindled for some people.
I think the Android userspace might count as a technology that's been shut down. When Android first came out, it looked a lot like a mobile counterpart to a Linux distro with Gnome or KDE, with built in simple open source apps, like music, photos, downloads, and notes (now Keep). Now all these apps are littered with tie-ins to Google, and Samsung and Huawei have gone off and developed alternatives because it's annoying to use these apps without fully buying into Google (same to a lesser extent for Maps and Chrome). This might be a stretch though, and besides this I don't know of any Google technology that was popular and useful and got shut down in a way that reminds me of Google Reader.