The tech behind wave eventually made its way into Google docs though and pioneered collaborative document editing, so wasn't a complete failure even though the product itself was killed.

No comment on Google+, Google has a storied history of failure on any kind of social media/chat type products.

Where Google wins is just simply having enough money to outlive anyone else. As the saying goes "the market can remain irrational longer than you can remain solvent" In this case, Google is the market and they can just keep throwing money at the wall until OpenAI, Anthropic, etc. go under.

Social media has strong network effects that keeps competitors at bay. What network effects are OpenAI/Anthropic/etc accumulating?

Yes, but Gemini is actually good and so are their APIs.