I would not say the "nobody saw this coming!" Legacy tape was soon to run out. The tape from China is very low quality.
This is the outfit making it.
This outfit is making ferric tapes, chrome and pure metal is best for cassette. I don't think they have been made for years.
I wish them luck. The biggest problem is the milling to get a good firm straight tape edge.
That is what Ampex was renowned for. Ampex tapes had a perfect edge so there was always good head contact.
The biggest use of cassettes is audio books for the blind. The blind have a lot of trouble with digital media for obvious reasons.
About 15 or so years ago I was part of an effort to preserve the old Ampex plant in Opelika Alalbama. When Ampex went under the plant was bought and operated by Quantergy. They went bust and there was no source of reel to reel master tape. Then an out fit in Holland had a brief existence. I was part of a group spearheaded by Peachtree out of Georgia to keep the Opelika plant going. We failed.
Then
ATR magnetics started up and have been successful keeping a source of reel to reel master tapes.
I had a sample from them. It is very high bias. The Revox A 700 could crank out enough record bias but my Brenell machine could not. I never tried the A77s.
Anyhow I have a hoard of the last Quantergy runs from the Opelika plant carefully stored. Trouble is there is not a need for it I don't think. After the closing of the Opelika plant putting together a DAW was feasible. Soon after that closing I built my first DAW. In all honesty I can't say I would do a reel to reel production again. I don't care what the Audiophools proclaim. The fact is digital recordings do sound better and working with it is a lot easier than rocking reels listening on headphones, making the splice point for an edit, and then razor blade cutting in the cutting block and putting it back together with splicing tape.
3db if you are interested I have quite a few BASF Cr bias unlabelled bulk duplicating cassettes. That was the remaining stock from the bulk duplication system I had.