I think it is far more complex than that. This is about who determines what is built in cities, and what account is taken of the opinion of locals (usually diddly squat). So fashionable it may have been, but I warrant that Brutalism was only ever fashionable at the architect/ developer/ council/ critic/ academic level, and never amongst the populace who had to live cheek by jowl with the buildings imposed upon them. I can't think of any architectural style which would so unify opinion as Brutalism.
I rode through Silver End this afternoon, through its famous collection of modernist houses. They're not fashionable houses, but they're also not hated in the way Brutalist stuff is. I'm all for preserving them, despite them not appealing to me very much. They respect tradition and the inhabitants of adjacent buildings by working at a similar scale as existing buildings, and by their relationship with the street and each other. Brutalism set out to deliberately stamp all over that sort of stuff, as, indeed, do many pieces of architecture today. I don't see any merit in that.
I rode through Silver End this afternoon, through its famous collection of modernist houses. They're not fashionable houses, but they're also not hated in the way Brutalist stuff is. I'm all for preserving them, despite them not appealing to me very much. They respect tradition and the inhabitants of adjacent buildings by working at a similar scale as existing buildings, and by their relationship with the street and each other. Brutalism set out to deliberately stamp all over that sort of stuff, as, indeed, do many pieces of architecture today. I don't see any merit in that.