Foldable personal accessories etc have been the requirement generally for over 60 years,
The fashion industry made that change for us from folding wallets and compact mirrors etc etc
What was missing for phones was the technology to replace slab formats that have almost grown too much now
So no sudden change just technology catching up with requirements for larger screen trends
Additionally as others have noted other convivences come with a fold, such as reading, people with visual impairments, single device etc