With the rise of social media sites that allow for the vast collection of data one people it was only natural that a company like Google that does just that wanted in on that game. So for them to want to establish G+ as a service is no surprise to anyone.
They way they did it however was pretty terrible and they deserved to fail. First of all they had to address the fact that some people are not going to want to join such a service; period. They don't want Facebook, never wanted MySpace, delete those annoying emails from LinkedIn, etc. They might know that they are not being given a service as much as they are being used as a product. Regardless of the reason why there will be some people that will not want, and resent if you try to make them, join such a service.
And with Google's campaign that was trying to force people to join G+ you built up resentment. A lot among the people who did not want the "service" in the first place and others who could have gone either way. The gamble Google was making here was that people would get over that resentment after a time because of how awesome G+ was going to be!
But forcing people to join the service was not enough. They wanted to make sure that this "service" was really a good product for them with their real name policy. The idea of giving out your real name worked for Facebook, and other services, because the whole concept of these social "services" was relatively new. People did not realize that they in fact were the product. By the time G+ was trying their hard sell enough of the population that might have been interested in G+ decided to give it a pass.
And that is pretty much were I think it stands now. Their track record with G+ is bad with their hard sell tactics and aggressive desire to make it a product for themselves rather than more of a service, people know exactly what is up with data collection, and other options exist that don't have such issues. G+ is a failure and likely never will be much more than that.