Brunei firm pitches 1,600 km high-speed rail linking Indonesia, Malaysia
https://asia.nikkei.com/Business/Transportation/Brunei-firm-pitches-1-600-km-high-speed-rail-linking-Indonesia-Malaysia
I guess this high speed railway plan came out, because high speed railway "Whoosh" succeeded to attract more and more passengers.
The problem would be lack of population in each city along the high speed railway. But, after relocation of the Indonesian capital from Jakarta to Nusantara, population will increase dramatically.