[dullgiulio]

I believe Wave was pretty similar to what Slack has become today. It was bringing a lot to the table, but probably too early.

Not too early for users to see the value, but for Google to roll out widely enough to make it a proper social network.

Technology was not mature enough for such an application.

[WorldMaker]

I don't the problem was the maturity of the technology (much of it very quickly migrated over to Google Docs soon after the Wave shutdown). Wave was built in the original Google model of an open garden; parts of it were based on XMPP (like Talk was) and all of it was designed to support multi-instancing and federation between instances similar to both XMPP and email. It launched just in time for the Google+ efforts to decide the future of Google was only in an entirely proprietary walled garden.