Hi folks, new member here!
There seem to be any number of threads on this, so I'll just jump in here to say that one thing I haven't seen discussed here is the impact the resurgence of new vinyl over the past however many years has had in the re-emergence of cassettes.
For starters, whereas new/struggling bands used to press 7"s to sell as tour swag, the backlog at pressing plants and the general uptick in expense has made that exceedingly difficult. Quite often if I go see a good youngish touring band the music they have to sell will be on cassette.
I also think the rise in prices for lots of used vinyl has spurred interest - it's just getting harder and harder to go digging for records and find anything that isn't priced stupidly. Most record nerds have had that moment when they dig someplace for hours just to have the clerk/owner check popsike (or i guess now discogs) to price the stuff! frustrating to say the least. Ha, this is not nearly as much a concern with cassette.
Now Justin Beiber or Adele on cassette? No clue.