Surely someone who goes to the toilet multiple times on the same flight would be recognised by a fellow passenger- especially if their toilet visit occurred within a minute of another fire breaking out. Perhaps the flight was not full and the culprit also playing musical chairs?
It's a shame the perpetrator couldn't be identified and thus charged under anti terrorism laws in Indonesia or UAE. Fire and aircraft are never a good mix. Sounds like the crew did a good job in quickly containing the fires.
I'm a little amazed that the flight was allowed to continue from CGK though if they couldn't identify a culprit after what had occurred on-board from MEL-CGK. Not sure what the answer is though- confiscating all lighters and matches from passengers as they pass through security and pat down of all passengers? A tough one for authorities. Thankfully, the flight ultimately arrived safely at AUH.