Back door colonisation nipped in the bud. Indonesia had a violent history with communism. The killings of all malay sultanates in sumatra was attributed to communists and nationalist. But I put this incident on javanese who didn't want sumatra to break free from Indonesia. The monarchs were friendly with Dutch colonialist and probably studied in Netherlands.
The execution of malay sultanate in northern kalimantan ( current location of new capital) confirm its the javanese/communists behind all the eliminations of malay sultanates. This was done later in 1960's as the monarch was deemed too friendly with Sabah government when it merged with Malaya.
Every move by jakarta neutralises any move to break away.