alt Hacker NewsI don't know how much the USTR campaign against TRON affected the success of BTRON, but I feel like we should be careful about this explanation. This is a classic example of American exceptionalism, but it seems like the USTR mandate just created a certain amount of FUD around TRON at best. You can see that it targets both BTRON (The desktop version TRON) and CTRON (the telco version of TRON), but unlike BTRON, CTRON did see real adoption and even dominance in the 1990s.
I think the main reasons behind BTRON failure like in the domestic market. I really don't know much about this period but here is my understanding. BTRON was never an OS, but rather a specification, a set of standards for how BTRON-compatible operating systems should behave. This is quite similar to POSIX, but the standard covered significantly more than POSIX (e.g. HMI guidelines and character encoding) and the BTRON standard came _before_ the implementations. But just like POSIX, there was no guaranteed ABI compatibility. And to make things worse, every implementation had to be rewritten from scratch, while most Unix distributions before GNU traced their code all the way back to AT&T Unix.
The other issue is that with BTRON1, the OS implementation seem to have been expected to be developed by the hardware vendor - they were not envisioned as highly portable operating systems yet.
The different OSs were supposed to be developed by OEM vendors and interated directly into their hardware (especially with BTRON1). From what I could find, only 3 vendors have signed up for BTRON: Matsushita (Panasonic), Toshiba and OKI[1]. As far as I can tell, out of the three, only Panasonic ended up releasing BTRON-based computers. Panasonic went quite heavy on TRON and released multiple BTRON products, but Panasonic was a minor player in the home PC market in 1990[2].
Another small company that picked up BTRON was Personal Media. They released a sizable variety of BTRON-based hardware during the years and eventually started releasing it as a software package. In fact, they're still active today, rleasing it as chokanji, running inside a VM on Windows[3]. They basically took BTRONs impressive Kanji support and pivoted to an IME allowing inputting Kanji characters outside of Unicode.
The names that are missing from this story are all the big players in the PC industry in Japan in the 1990s. It's obvious why IBM Japan wasn't onboard, but NEC had its own monopoly to protect and Fujitsu and EPSON were clearly not interested[4]. CTRON, on the other hand, was picked up by NTT, which is probably the only company that mattered in Japanese telecommunications back in the early 1990s. BTRON had a window of opportunity in 1990, since Japan (or the rest of the world for that matter) did not have a dominant GUI platform yet. But in a market where the OS came with the hardware, lackluster vendor supported kinda sealed the deal.
[1] https://qiita.com/ko1nksm/items/243865903ae48c2c2c29
[2] AFAIK it was heavily dominated by NEC, with the smaller players bein Toshiba, Fujitsu and Epson. In 1990, when the first BTRON implementations were released, the dominant standard was PC-98, which was developed by NEC, with Toshiba and Epson making PC-98 clones. Even though all these computers were running x86 and usually ran on MS-DOS, they were NOT compatible with IBM PCs. This is mostly due to IBM PC not having enough RAM to display Kanji, so the which Japanese PC manufacturers in the 1980s solved with custom Kanji ROM chips. Getting Kanji support throughout the stack also meant heavily modifying MS-DOS and producing a different software stack that is tied to the custom hardware.
1990 is also the year that both DOS/V (a localized version of DOS that had built-in Kanji support) and Windows 3.0 were released, and both of them eventually lead to the death of domestic Japanese PC standards, since they could sufficiently support Kanji in software. 286 and 386 based PCs with extended memory were also powerful enough now to support Kanji in software, and DOS/V and Windows provided a standard application runtime environment for that. But this eventual standardization took time and back in 1990, PC-98 dominated the home market, while IBM managed to get some corporate market share with its PS/55 (an IBM PC variant with a custom display adapter with its own Kanji ROM).
[4] OP happily mentions NEC, Hitachi, Mitsubishi and Fujitsu, but it fails to mention that they joined other TRON initiatives (ITRON, CTRON and The TRON chip) and explicitly declined to join BTRON.