For me the decline began when Ruth took over from Patrick, and when the whole Alphabet-ization thing was (clumsily) executed. It was clear at the time they had no idea what they were doing. At all-hands Larry & Sergey couldn't answer basic questions about the strategy and how it would affect large parts of the company (I was in the 'Access' PA at the time -- the PA that ran Fiber, and launched Google WiFi, et -- and Sergey didn't even seem to get that it existed,). They had mentally checked out, and it was obvious.