The article doesn’t really do a great job of answering the titular question. So … Is the answer “mostly because of policy failure”? Because that is what opening two coal plants in 2024 sounds like to me.
I’m also a little confused how they managed to jump from “renewables are making power cheaper in Japan” in one paragraph to “this is hampered by G7 liking fossil gas” in the next paragraph. (I do share their worry about G7 nations investing in fossil gas too much. My home country Germany has just introduced a gas peaker plant strategy and appears to be over-investing in LNG terminals.)