Among many justification for socialism, this one actually make sense. The ming and the sung in china also fall due to wealth disparity.
The poor, which has no land to defend anyway, don’t bother fighting. Government then perform a belated response of redistributing land and confiscating property for “national defense”. This results in the rich switching side to mongols.
However, most socialists measure simply worsen poverty. Socialists take money from workers via income tax, while giving it to aristocrats and land owners via bribes, infrastructure building, and corruption.
But if that’s our only point of view, we won’t see what’s really going on. We won’t see, for example, that we too would at least be very tempted to do the same thing under the same condition. We don’t see that most people would do the same thing. In fact, if very few people would do the same thing under the same shoes, we’re not facing a great evil.
Understanding rather than simple condemnation works better in most cases.