Earlier quoted context omitted.
Google has massive range and tons of way to push their services onto users, and google+ failed miserably. Resources are not guarantee of success.
I'm convinced that what killed Google+ was their slow rollout, which was an absolutely bone-headed move that I'm really surprised a company like Google would make. Google+ was a social network. For a social network to have any value, you need your friends to be on it as well. By making it invite-only and throttling how many people could join, they guaranteed that most of your friends weren't there and COULDN'T be the…
This helped build word-of-mouth. While a social network has value, so does an exclusive nightclub with a long queue around the block to get in.
I've no idea, but I wonder if this was the thinking behind Google+. Build up a demand with artificial exclusivity, so you build buzz (maybe "buzz" is the wrong word, given Google's other dead project of that name). This approach also helps you from the technical side - easier to deal with scaling and other teething issues when you have a few users at once rather than the mad rush.
At the end though it was probably the wrong decision - people were already on Facebook so they just shrugged and forgot Google+ existed.