I remember MiniDisc not going anywhere beyond a small clique of enthusiasts and the data version never getting anywhere at all - the reasons why are pretty much set out
in the Wikipedia entry. Also, there were already several other magneto-optical disc formats around before the Data MiniDisc - I remember using 3.5"/90mm M/O disks (not MiniDisc) in the early 90s and there were 5"/130mm versions widely used for CD-ROM authoring in the days before cheap CD-Rs.
Steve Jobs' NeXT cube (arguably more the ancestor of modern Macs than the Macs of the day) used a 130mm Magneto-Optical drive.
I was always surprised that Sony never pushed MiniDisc as the obvious replacement for their 3.5" floppy - but they went with an optically-tracked "floptical" instead for the sake of backward compatibility. Plus, there was no "king maker" that could anoint a new drive by building it into their PCs the way IBM and Apple did with the 3.5" floppy in the 80s: in the mid 90s, IBM were effectively dead as a PC maker, and Apple were at their lowest ebb. Oh, and DOS PCs still needed a floppy drive as a boot medium - even booting from CD, where available, used a floppy disc "image" on the CD.
Then CD-R took off: a
horrible medium for storing data but with a price-per-megabyte that made it a no-brainer.