As I understand it, GChat wasn't seen seen as able to integrate well into G+. So Hangouts was built on the G+/social infrastructure.
To that team's credit they did somewhat seamlessly move users over from GChat to Hangouts without many hiccups.
Of course, after the G+ effort disintegrated... we got Allo & Duo
I don't think it's a bad thing that google ha a diverse set of products that didn't work together. I don't need my google calc/excel to integrate with youtube, and I don't need google play music to integrate with gmail.
Google should look at these things as individual companies, which it seems like is something that they finally somewhat figured out with the alphabet rebrand. Just let gmail be a successful company on its own, and let youtube be a successful company on its own. From my perspective as a user, things actually get worse when all of these things try to play together.
That makes sense to an extent. Unfortunately, Google has created a number of products or "companies" with overlapping features that are in direct competition with one another. Just in the communication space, they have: Hangouts, Gmail, Inbox, Allo, Duo, Messages, and Google Voice.
These actively compete with one another and make the sum of all the products worse than just one good product. If I want to send an SMS message, I can currently use Hangouts, Messages, or Google Voice. I don't want to decide which to use, and I certainly don't want the one I choose to just disappear one day while I get booted over to another app.
Specious?
What is Social? Is that at major product vertical within Google? "Possibly" is a potential good answer here :).