> Could anyone in 1990 have predicted the smartphone

Yes. It was called a communicator in fiction of the day. Did they get the exact details right, or every use case (e.g. replacing flashlights and music players)? No. Some of them used holograms from watches or big old handsets with a screen instead of a keypad but still big ear cups. But a portable device that could be used for voice calls, video calls, information lookup, note taking, certainly existed in fiction prior to the 90s.