This is good news. Nest had a groundbreaking product and Fadell failed to capitalize on it and design and produce a coherent ecosystem of home products. Anyone who has a security system at home knows how clunky and badly designed most of the components are, and most of them had Nest redesign written all over it. Nest had hardware with motion detectors (both Protect and Thermostat) and Dropcam for a while, so it should have taken them no time to produce a coherent and comprehensive security system solution that would tie into the existing Nest ecosystem and blow everything else on the market away. Instead, there is no such security solution on the horizon, they cannot even make a sealed Dropcam that you can install outside the house (despite constant pleas for that kind of solution on all the forums). It is a very large market that Nest missed ( and once people install cameras on their houses, they are not switching, becuase its much harder than changing a thermostat or smoke detector).
Fadell also failed to capitalize on Google's software might, preferring to do everything in-house, with predictable results. Add to this persistent rumors of arrogant behavior and difficult corporate culture at Nest, and you start understanding why this news has been long overdue.