Google's founders used to be quite "deeply involved" in the day-to-day business, and the company didn't suffer for it. Maybe this has something to do with it becoming "unrecognizable" shortly after they checked out altogether.
My guess is that they did this because they saw Facebook as an existential threat of sorts for Google. Maybe you feel that the whole thing was badly managed, but it's hard to say this other than with hindsight. G+ was no Facebook, but it looked like something that could be successful for quite some time.
