Cynical thought: in no way am I claiming this was the only reason for Microsoft choosing Blink, but it’s probably easier to find and replace Google analytics APIs with Microsoft endpoints than it is to add them into a code base after the fact.
Edit: Chromium connects to Google servers to update extensions and for captive portal detection. Firefox does pretty much the same.
(note that I think there's nothing wrong with this at all, just pointing out that this isn't chromium-specific)
Both chromium and Firefox can be customized and vendor branded (see the countless privacy oriented browsers built on top of Firefox).
That's pretty misleading. When you want to sync state across Chromium installs, you use a Google account, and that's really just scratching the surface.
Chromium comes with quite a bit of Google baked-in.
Iridium was developed specifically to degoogle all attempts at phoning home.