Thank you for the question. I don't think I will be able to do it justice for the response, because I confess that I have never been to Toyama, although I have lived in Japan, and I've probably been to many similar cities. I would like to immediately suggest you go to their website. If you search for the name you can probably find some information about it.
Let me try to answer the question. First of all, they were facing several problems at the same time: a clear economic decline, loss of the young people, and a concomitant demographic shift. The city was growing older much faster and they could tell that they were not going to be able to supply the city services any more. They just could not afford it. It would bankrupt the city. There was a pressure at the municipal level that they had to do something in order to make the city more attractive. They did have a little more pressure than we could exert in North American cities in forcing the location, or relocation, or realignment of some of the major infrastructure items, such as the hospitals, senior citizens homes, and so on, in a way I don't think we've really tried to do.
At the same time, we have the influence of the environmental movement where they knew that they needed to reduce their carbon emissions. This is a general agreement in Japan that they have to do something about it. So it was a constructive confluence of both the positive and negative trends that they had to deal with, and they realized that the best way to accomplish it was to begin reshaping the city. It's not finished. It's a work in progress. I use it to illustrate the kinds of concepts that might happen for different reasons. You may end up finding yourself saving lots more energy, but mainly to address a completely different problem.
I suspect I'm slightly avoiding answering your question. I encourage you to make a field trip to Toyama City and experience it for yourself.