The compact cassette hung around for a few years while it had advantages over CD (recordable, usually quite cheap, portables readily available) - even into the mid-90s they still covered a few cassettes in Penguin. Vinyl OTOH had no advantages over CD, thus demand in the classical sector dried up very quickly and supply stopped accordingly.

Yes, definitely - he was well known for being a serious technology enthusiast and during the 1980s (the last few years of his career) he was hurrying to re-record a lot of the repertoire digitally for posterity, a body of recordings which now forms the Karajan Gold series from Deutsche Grammophon. You could argue that he conducted like an audiophile anyway - he spent decades developing the distinctive weightily opulent sound of the Berlin Philharmonic from the rostrum. I think it's fair to say that he probably knew what an orchestra was supposed to sound like, at any rate.