Historical Computers in Japan

The main issue? Using the 6809 CPU.

At the time, the 6809 was a "dream CPU" - compared to lower cost rivals like the Zilog Z-80 and MOS 6502, it had a set of features (more registers and such) that made programming it much easier and resulted in a more powerful system.

A popular operating system of the time for machines using the 6809 processor was Microware's OS-9, which allowed for multiple processes and multiple users on such machines; kinda like an 8-bit form of Unix - but lower priced.

Low-priced enough that Radio Shack sold a version of it for their 8-bit 6809-based computer - the TRS-80 Color Computer - called OS-9 Level 1 (later, Level 2 would be released for the Color Computer 3 - today, an open-source version can be had called NitrOS9 - while Microware is still in existence, they don't support or sell the old 8-bit versions of OS-9 any longer).

Like the 8-bit FM computers, though, the Color Computer didn't do well in the US market, because again...it used the 6809.

The 6809 was an expensive processor, compared to its rivals used in most other personal microcomputers of the time; consumers as always were price conscious, and went with the lower priced options instead, in most cases. The 6809 found more success in the business and commercial embedded space, where price was less of a concern, and performance was more valued.

As an aside, the 6809 enjoyed a fairly long life, and later Hitachi came out with a pin-compatible version that included some upgrades, the 6309, that can help to speed up software that uses them - as a result, many people upgrade their Color Computer systems to use this newer processor.

So that was Fujitsu's misunderstanding of the market - that people would put performance over price at the time when it came to CPUs. That wasn't true in the US for most people.

Their second mistake?

Including a second 6809 CPU in a multi-processor configuration.

If one 6809 was considered a "mark of doom" for a personal computer of the era (for the US market) - two was seemingly unthinkable to all but a very few enthusiasts (who also had the money to burn). Similar offerings were made in the TRS-80 Color Computer market toward the end of that line (late 1980s to early 90s), with the idea of luring OS-9 users and hopefully others, but few went that route (that, and the 68k was also a draw - but it had a fairly short life in the consumer market, too - mainly limited to the Amiga, Atari, and Mac - then later to some console game systems).

Ultimately - well, we all know where and how things ended up.