/gd/ — Sorry if this is not the correct board, but it seems the mos

since you immediately came crashing in with this as a subject, frutiger aero is not a real style of the time, it is a contemporary piece of nostalgia
in general art is always derivative, all art is using other people's references (or referencing the world) and other people's styles, taking what you like and filling in your own ideas into them. this means that there are certain movements, certain things people like to copy, certain novel combinations of ideas that people then copy, and this is what is studied and made into meaning "styles"
the style you're talking about is one that was mostly made through the novelty of being able to apply humanist character to user interface design; before then, it was impractical to give user interfaces glossy icons and borders because rendering those in real-time was not feasible. when technology started allowing it, people flocked into the new grounds and often sort of overdid it
this is also why flat UIs later overtook, mobile phones and laptops brought in screens with massively different scaling factors, meaning that you'd have to create a bunch of copies of all your nicely-rendered glossy UI. in comparison, vector graphics had become performant enough and solved this issue by design, at the cost of being usually very flat. that push was mostly started by the excellent Matias Duarte who did design for Android at the time, designing Holo design, which then kicked off Apple to do the same. the interesting thing is that where Holo went into a more industrial grotesk design, Apple decided to keep their humanist ideas, and that's what won out in the end (Matias then pivoting to Material Design which was a humanist rendition of Holo's ideas)
right now we live in pretty exciting times in UI land actually, where computers have become powerful enough to do arbitrary non-rectangular layouts, and the grip of humanist design has started fading drastically