Coal is not just for electricity, more importantly it's also vused for smelthering metals like steel, iron, etc. With the Indonesian planning to move their capital to Borneo, tons of steel is important for building vital infrastructure.

Traditionally, Indonesia is poor, corrupted and mainly agriculture based. Most exported resources are processed by developed countries, or the govt was too poor or unstable to develop their mines. However, things are very different now, the govt is relatively more stable, there is tons of FDI flowing in, booming IT and private sector, better education and abundant cheap workforce.

There are many vital metal mines in Indonesia, but more importantly for them the EV and tech boom has driven some of the prices of those metals to skyrocket, which makes it a lot more economical to open their mines now. The other good thing the Widodo govt did was to ban export of metals, meaning companies vying for those metals are forced to build factories in Indonesia like Hyundai, some Chinese EV companies,Tesla etc to name a few. It will create jobs, growth, tech transfer, poverty alleviation, etc.