You can see me in the vid
IMHO - Jetstar's big problem was loyalty program.
SQ/TR both seamlessly intertwine with Krisflyer.
All other premium carriers in the region have a proper loyalty proposition.
Air Asia's loyalty is beyond pathetic, but they're known as the lowest cost (even though they're not).
Therefore Jetstar Asia was stuck between being a premium version of Air Asia and a full service carrier in terms of loyalty.
Before anyone chimes in about QFF - Nobody outside of Australia gives 2hoots about QFF, and therefore - you'd only end up on jetstar if the cheapest option, or the best option were not available.
A standalone Jetstar loyalty program based in Singapore - to grow their regional presense beyond being a quasi Qantas feeder airline, would have made a big difference IMO.