Currency debasement and ethical decline
Discussion
I hear currency debasement has been the declining factor in a few civilisations, states and empires. So it's a believable answer... How does ethical decline fit in?
It enabled the currency debasement, also enabled the runaway debt due to overspending on unethical things such as war, nanny state, Intel complex. It's a feedback loop. This then began to permeate many segments off society because of embracing of the lack of ethics by academia. They replaced ethics with relativistic fake morals.