Well you do know that Sony also publishes music right? Sony wasn't inclined to support MP3 anyway.
The thing with minidisc, when using the NetMD thing that let you record digitally direct from a PC, wasn't just ATRAC, it was
(a) you couldn't easily upload tracks recorded on a portable player/recorder to a PC,
(b) the ridiculous restriction that meant you couldn't even delete or reformat minidiscs that had been recorded from the PC, unless you connected it to PC again and 'checked back in' every track on them first.
(c) you were only allowed to 'check out' your tracks ripped from your own cds to your own minidiscs three times.
Such a stupid attempt to lock the stable door after the (napster) horse had bolted. Damaging Sony the hardware company for no real benefit to Sony the publisher.
Wasn't it also Sony that got done for illicitly installing SECUROM style DRM software on PCs from their cds, without notifying the owner?
The whole industry really lost their minds over mp3s, coming up with 'solutions' that caused far more problems than they solved.