The rich, cheating soliders out of land that was theirs by law, custom, tradition, and right, destroyed the middle class and centralized wealth in their coffers. In the ensuing troubles demagogues rose; some of them well-intentioned, some less so. The lower classes factionalized.

Macaulay is saying, quite simply, that this kind of selfless action can only happen in a society that's well. Where people give a shit about each other. Where the poor are maintained, and the rich (and those in power) know their place is to serve. Picking up a little later: ---