[catiopatio]

I don’t recall that being the case, but my memory could be faulty.

As I recall, the High Sierra Format - which served as the basis for ISO 9660 — was widely used prior to ISO 9660’s standardization and adoption.

[astrodust]

Widely, but not exclusively used. Some big vendors at the time that made things like library indexes and legal references used their own completely wacky in-house formats that required lots of fiddling with device drivers. They'd often only work with a handful of CD-ROM devices as well, meaning you're stuck with your $2000 single-speed top-loading NEC drive for eternity.

High Sierra won out, it was the logocal winner, and there was, thankfully, no standards war like with HD-DVD vs. Blu-Ray.