I came across this 2015 article in Mashable by Seth Fiegerman on why and how Google jumped into the Social bandwagon, created a non starter and sort of Me-too product, copying Facebook and lost the plot. It is a back story of how Vic Gundotra, then close to Larry page, built up a threat frenzy within where apparently none existed (at this point FB was valued at 14B and Google 200Bn – not any more). Although the security lapses gave the immediate reason for Google to decide on shutting down G+ the broader issues, primarily of non adoption, and blowback for coercion ( remember when you had to have a G+ account to sign into other Google services?) hastened the end.