Some of these are a bit spurious. I mean, Venkman was replaced by Firebug, which was much better. MXR was similarly replaced by DXR. Unlike Google, which look much more arbitrary in their shutdowns, Mozilla typically kill projects that are already on their last leg, or replace them with something objectively better.
To be fair, I think that logic applies to some of the items on Google's list too. Like Google Nexus? They changed the name and scope of their phone line. AngularJS? They took the framework in a different direction.
The targeting of the Nexus line was completely different to Pixel though, they could easily have co-existed. And there was a gap between them. I've never worked for Google, but I assume 'kill Nexus' and 'launch Pixel' were independent decisions, the latter unforeseen at the time of the former.