Facebook had lists (don't quote me on the name) which was very similar to Circles, without needing to be on the sahara desert of content which was Google+.

The advantage of FB was also that you saw content, whereas on Google+ everyone would have it locked up and you couldn't see it, great for the less popular types.

This comment reminds me of Google wave too.

Parts of it made sense, maybe a bit too early, not enough people using it.

I thought extra Instagram accounts are used as pseudonyms, which G+ was never willing to accommodate.

Instagram only implemented "close friends" after years of a solid user base to research the usefulness of that feature. It's not that they couldn't think of it; ideas are cheap. A lot of it has to do with the stories feature, an innovation stolen from Snapchat that G+ predates. And G+ Circles was way more complicated.

Circles feature was also marketed the wrong way. The G+ ad showed a lady bad-mouthing her boss in a circle that doesn't include him. Who's gonna put that much faith in the separation? The entire point of a finsta is that it's not a supported feature, so you can believe that it's totally separate and also has a different name. You'd use the finsta to bad-mouth your boss or perhaps even less wholesome things.