Denmark has done the same with the word “Hygge” and you’ll find books named “hygge”, next to books named “ikigai” in self-help section of any airport bookstore.
I don’t think discussing ikigai is uninteresting, but there is a feedback loop. Japanese soft power benefits from ikigai being special, and books and articles about ikigai also benefits from it being unique and special. The more books you can sell on ikigai, the stronger Japans cultural influence becomes and as a result, the potential readership of ikigai book grows.