The age reports the discovery of an ancient civilization in modern Cambodia. They used advanced technology to find it and it lay buried under the jungle unknown to the locals. Because of that, it hasn’t been looted. The civilization lasted for 600 years. Not quite as long as the Northern Levant (now modern day Lebanon and Syria) which saw 12,500 years of prosperity before its sudden demise. Demise is always sudden. Things break much faster than they are built. Observationally, you can see that cultures, which are mostly free when it comes to commerce, that are small in size last longer than empires. The bigger the country, the higher taxation and resource usage, the more likely it will collapse from some external, sudden shock. Big states are fragile. The United States could be completely gone in 25 years. It wouldn’t take much of a push, another bank panic perhaps or collapse of the dollar.
If you read the article at The Age, they indicate that the inhabitants practiced slavery. That seems anathema to those raised in the West but that is just a state mind a cultural view which is a hold over from Christianity. Eventually as the drift from Christian culture continues people will start to ask themselves what was so bad about slavery? A little bit could be good for the underclass. Ancient evils never die, only the people who practice them.