I think there are multiple separate events here, timed to coincide in order to minimise disruption. It's hard to be sure whether they share overlapping causes, but I'd guess that there's at least an element of that.
Isn't it "just" a matter of Jeff Dean (& co) leaving, Hassabis replacing Dean, and Kavukcuoglu replacing Hassabis ?
A massive shake up for sure, but why do you see it as separate events merely timed to coincide ?
Yes. In public relations you never want to trickle out bad/concerning the news, you want to "rip off the band-aid and preferably follow it up with some positive/distracting news like 3.5 Pro model release or price drops.