...there has been a moral collapse in the West. The moral collapse preceded the propaganda which in turn nourished the moral collapse. The enemy is both within and without, but mostly within. We renounced the moral code of the past many centuries (you could say five thousand years, beginning with Abraham), for reasons that have not been definitively clarified, though there is much speculation. If better people cannot win back their cultures, or at least secede from the enemy to form new States, then there will be no future for the West. However, I try to remain "on alert" - on the lookout for good signs, such as the recent elections in France and Europe. And the Internet prints the truth which must have some effect in the long term. An economic collapse can always be overcome, but a moral change, a mutation, is much more difficult to comprehend.
There's much merit in this answer. The Western intelligentsia was sickly as far back as the early 1900s (remember Randolph Bourne). It lost the connection to the great values that had once inspired Westerners, and once this emptiness became apparent then it was inevitable that there would be a fall.
But what brought about a sickly intelligentsia? I'm not sure that you can isolate one single reason. Some people go very far back and blame the rise of nominalism in philosophy, namely the idea that there are only individual instances of things and that universals do not exist.
Others take aim at scientism, the idea that the only valid knowledge is that acquired using the scientific method (which means that only concrete, measurable entities are taken seriously).
Western philosophy also took a turn toward scepticism, in which there is doubt that we can have true knowledge of external reality.
It seems to me, though, that the early forms of liberalism are partly to blame for setting up the fall. The idea that society can be organised around the pursuit of rational self-interest in the market cuts right across the older ethos, as does the view that the good can be relegated to a private affair within the civil realm whilst the state remains neutral.
The Anglo cultures were also hamstrung by a tendency to include liberalism itself as part of the ethnic identity; if you believe that being liberal is part of being Anglo, then how do you give it up when it becomes clear that liberalism is undermining the existence of the Anglo peoples?
Finally, the strongest and healthiest current within Western cultures was the one which fused Christian and aristocratic virtues. Whilst this current remained strong, it could keep the West afloat. But in parts of the West both Christianity and the aristocracy went into decline in the late 1800s and early 1900s.
It's true that Christianity retained popular support for much of the 1900s. But the Western intelligentsia had mostly dropped away from Christianity by about the 1880s; and the position of the English aristocracy declined markedly from the very early 1900s.
The problem, then, was both a decline of the healthy current and the existence of a number of competing currents which were incompatible with the older values.
One final point to make is that it is difficult to simply blame the left for what went wrong, as the modern left grew out of the demoralisation rather than bringing it about. In other words, the modern left is more a consequence of the decline; it is what emerges when things have already hollowed out.