I was not involved in this project, but I have previously worked at Mozilla (although I left over 3 years ago). Maybe I can share some high level insights for

I was not involved in this project, but I have previously worked at Mozilla (although I left over 3 years ago). Maybe I can share some high level insights for how these things are approached. Generally there are specific feature expectations when new platforms are added, and it can be a fairly major work. Besides rebranding, there are likely UI changes for look and feel, as well as specific capabilities expected across all platforms that were probably missing. Project deadlines tend to be soft deadlines rather than hard deadlines, but they are created to provide a point to work back from and define scope, and the goal is always to hit the deadline for release. Every day you don't release is a day users don't get access to the work you've put in. I seriously doubt Mozilla purchased a Superbowl ad or otherwise had financial reasons to set this deadline.