My comment is more to you talking about trains in general, as there are already regular trains in place. This is more about where high-speed rail fits in. AP News also has an article on it:

“I’m so happy and very excited that finally we can ride a bullet train in Indonesia,” said Christianto Nusatya, a Jakarta resident who joined a public test ride last week. “But still, I would prefer to choose a regular train or car, because Jakarta-Bandung is too short and not worth it to be reached by high-speed train.”

Deddy Herlambang, executive director of the Jakarta-based NGO Institute for Transportation Studies, said the public does not really need a high-speed train on the Jakarta-Bandung route because there were already many other ways of traveling between the two cities.

He said the bullet train would have a significant economic impact if it connected Jakarta and Surabaya. However, he was pessimistic that the railway project would make a profit in less than 30 years of operation.

“The high-speed train cannot replace the old transportation that previously existed,” Herlambang said, “People, of course, will prefer to use far cheaper modes of transportation for short distance trips.”

https://apnews.com/article/indonesia-southeast-asia-highspeed-railway-e7a53ecbcb077b4403d9232e7b93bcf3