They boldly claimed they'd beat Facebook in 100 days and began acquiring any startup that pretended to solve a social problem. Every team got a G+ OKR. In classic Google fashion, they chewed up the one social platform they had, Orkut, and gChat, which was filling the AIM void, also squandered its lead as it was subsumed. They never invested enough in their successful/functional video chat, and instead just had team after team launching new versions of the same damn thing. Looking through GCP and their AI/Vertex/Whatever naming soup, not much has changed.

Wave was very simply modern email. Conceptually, there's nothing more to it. It was a new protocol that effectively filled the same basic needs as email, but left room for first class support for the types of features we've either hacked badly on top of email or still lack today - proper threading, traceable message amendment, rich messaging & multimedia support that's not a MIME hack & an improved security posture.

I think that was maybe a secondary problem with Wave: it was marketed as some new voodoo that ended up smelling like a hammer seeking a nail, when it was really just Email 2.0

Loss of Windows Phone is sadly Microsoft's own doing.

They were around 10% in Europe when they ramped down everything.

It was the option for those unable to buy iPhones, and not willing to use Android as alternative.

However we had the whole mess with Windows 7 to 8.0 being a full reboot for devs, 8.0 to 8.1 being a reboot, 8.1 to 10 yet again, which naturally meant no one cared with quality apps as well.