[Clamchop]

Minor nit, cassettes were and are mostly worse audio quality than records and they coexisted for decades with their respective compromises. Cassettes replaced 8-track in the portable space and eventually enabled the Walkman.

CDs killed both.

[prmoustache]

CD didn't really killed cassette. They coexisted peacefully for 2 decades. CD was nice, transportable but cassette was still more convenient to carry around because a walkman was much smaller[1], wouldn't skip when running/jumping[2], a cassette was less fragile and it was simply so much easier to leave a cassette in a deck and record anything you would ear on the radio on the go. Virtually nobody could/would live burn a dj mix from the radio.

Napster + portable mp3 player and smartphoned did kilómetros ll the cassette.

[1] especially the late 90's early 00's ones that were barely bigger than a standard cassette case.

[2] there was buffering for discmans but it wasn't 100% effective if skipping happened for longer than the buffer