Google announced a new feature of Google Now at I/O this year called Now on Tap. It hasn't been available in any of the Android M developer previews, but it looks like one of the more exciting things to happen to Now since its introduction in 2012. Most of the original Google Now developers won't be around to see it, though. According to Re/code, many engineers that helped make Google Now a reality left in the months before I/O.
So, why? According to sources who spoke with Re/code, it mostly stems from a decision to move Google Now from the Android team into Search. Basically, emphasizing Now as part of Search (which is baked into Android) rather than a mobile-first feature. Several members of the engineering team objected to the move, but Android/Chrome head (and now CEO) Sundar Pichai approved it anyway.
Some former Googlers assert that Pichai doesn't place as much emphasis on Now as Larry page did when he was more involved. This feeling has led to only a single original member of the Now team remaining on to this day. Two of the main engineers behind Google Now's creation left in March, followed by several more leading up to I/O.
People leave jobs at big companies for all sorts of reasons, and certainly politics is often part of it. You have to expect things like that. However, moving Google Now under search could have major impacts going forward. Things are bound to change with a new CEO at the helm. We'll just have to wait and see what that means for Google Now.