I wouldn't say marketing so much as Microsoft did a lot of usability testing back then where psychologists threw people in a room and took notes while they interact with the UI. I don't think any OSS projects have this luxury (or money needed to throw around for that sort of thing).
Also, back then, you had to make the best with the resources you had. Computers were slow so UIs had to be lightweight out of necessity. Yet here we are in 2022 and GUI applications have become so bloated they take longer to open up then they did in the 90s. And yes I'm looking at you, GTK and Windows 'Modern' apps.
The Gnome project performs usability tests pretty often. That's what led to decisions like deprecating the secondary app menu (app menu in the title bar) and the newer horizontal workspace layout, iirc.
And the Gnome project consistently gets it wrong because they keep forgetting their primary target users are not rando's that have never used a computer but mostly season Linux vets.
Raymond Chen vaguely references it here https://devblogs.microsoft.com/oldnewthing/20120126-00/?p=84...
Also, back then, you had to make the best with the resources you had. Computers were slow so UIs had to be lightweight out of necessity. Yet here we are in 2022 and GUI applications have become so bloated they take longer to open up then they did in the 90s. And yes I'm looking at you, GTK and Windows 'Modern' apps.