This is just my hypothesis, but I believe the language barrier is an issue. English is effectively a necessity for programming because real programming languages with ecoystems, error diagnostics, documentation, and useful articles/blogs/books are written in English. Japanese software developers know enough to get by, but they're still by-and-large insulated from the Anglosphere learning culture, where ideas and best practices rapidly propagate in the open. I'm not involved in hardware, but I'm guessing this is less of a barrier for hardware because hardware/documentation tends to be proprietary rather than open anyways, so whereas the Anglosphere gains a cumulative learning advantage from an open source + technical blogging culture in their fluent language, this does not manifest so much in hardware.