[Google got] into open source software and it seems those survived the experience
Not really. Google is responsible for the open source browser Chromium, which is the base for Google Chrome, Edge, Brave, Opera, Vivaldi, etc. They dominate the browser market, and they use their position to implement features outside the web standard. Their competitors (mainly Firefox) are not able to implement the non-standard features, driving them out of the market. Classic Embrace-Extend-Extinguish.
Google got into the Linux space
Technically, both Android and Chromebok are Linux-based. But Google has done everything possible so that they aren’t part of the “Linux space”, to the point that Android uses a fork of version 3.x of the Linux kernel (regular Linux is now at version 6.x).
“Explain how Google would impact XMPP servers if they defederate from Google Talk”
Spoiler: They can