Reports suggest the Turbo Caribou was tracking IMC towards Jila Pass, a particularly inhospitable area in VMC, let alone IMC. The coordinates suggest they missed the entry to the pass by about 1 nm and if following cruising levels 500 feet below the top of the terrain they've impacted.
It's quite pathetic that the FAA raised Indonesia to category 1 when it's clear that the regulator is just as toothless as ever and operators are going to continue to lose airframes and lives.