I think its interesting that the flat look was pioneered by Microsoft going back to the days of the Zune2 and later lumia phones that had the first Metro interface. Then google and Apple and everyone else started following. People don't think of Microsoft (and especially Zune...) as a leader in design, but I think they have had a big impact on the industry, and deserves some recognition.
Metro was minimalist in a highway sign sense - less color, lots of emphasis on text and distinct shapes/outlines. I don't think flat designs we have now are all that similar.
I think you can probably trace some influence even further back to webTV. Check out its flat "10-foot UI" from 1999: https://youtu.be/eHJN9cMo4P4?t=156
And then in 2006 (per Wikipedia), "Xbox 360 overseer J Allard ran the [Toshiba Gigabeat 1089] project, codenamed 'Argo', staffed with Xbox and MSN Music Store developers who worked on 'Alexandria', finalized as Zune Marketplace."
Not at the moment, but the design elements are similar enough to the ones I'd see on my satellite receiver OSD menus from back in the early 2000s. I could tell that those were 3D as well at the time, and my TV at the time was a fuzzy 36" CRT from the 1990s.
And I'm glad for it! 3D design elements make a lot of sense on those kinds of displays, because they work well to stand out despite the relatively low resolution and color contrast.
The skeuomorphic to flat transition that the Windows Phone did was beautiful and groundbreakingly different. I loved it. Shame about the rest of that OS.
You don't get credit for being the first, you get credit for being significant. Zune and Windows Phone didn't get "people" into flatter aesthetics, Apple did.
After Windows 95 came out, fucking everyone used Franklin Black in their advertisements. I saw it everywhere -- online, on billboards, in television advertisements. Microsoft may have the aesthetic tastes of a lame, "greetings fellow young people" dad, but they were the biggest name in the tech field... and that meant people copied their design language in the hopes of seeming equally big and important.
