Indonesia never had high grade nickel ores, they have mostly laterite ore deposits, which require High Pressure Acid Leaching (HPAL) to extract the nickel, a process that became economical only about 10 or so years ago. Prior to this, the preferred ore was sulfide ore which was processed using conventional methods which were less energy and initial capital intensive. Non Chinese mining companies like Sumitomo and Vale spent fortunes in developing projects like Ambatovy in Madagascar and Goro in New Caledonia which are both considered failed projects as they will never give a positive ROI at this point. Chinese companies were able to make a breakthrough in HPAL technology which made Indonesian projects viable.