Everyone was preparing in advance, and those who didn't prepare adequately, or didn't prepare at all, naturally become targets of attack and exclusion.
Any family that had a prodigal child who only knew about pleasure and did not prepare for the family's future were left to fend for themselves - they had it coming.
But not this time, this situation is unique. The predicament has not been brought about by family mismanagement.
Natural and man-made disasters arrived together, small nobles without substantial assets couldn't survive this turmoil. It's no surprise that their resources ran dry.
In the world of the nobility, apart from the naked brutal realities, human feelings matter too.
Besides, there are proactive neighbours to compare with. If they were completely ignored, those younger brothers who couldn't withstand the pressure might switch sides and follow Hudson.