explain the irony of the final single commandment.start with what it means

Napoleon has rewritten the animals’ history to the extent that they feel they no longer have one. He has also manipulated language to the extent that it is meaningless. We see this reflected in the maxim, “All animals are equal / But some animals are more equal than others.” The concept of “more equal” is mathematically impossible, but the animals are too disillusioned and brainwashed to notice. In all the years since the Rebellion, not a single animal has gotten the rewards that he was promised or that was experienced so briefly in the days immediately following the Rebellion.

The irony in all of this is that everything Old Major warned the animals against in Chapter One has now come true. The rebellion was in no way what he intended.... the aninals had simply traded one form of tyranny for another.