what how

Four legs good, two legs bad

"Four legs good, two legs bad"
Come together animals, the pigs said
By this big slogan, the animals were led,
To overthrow their human oppressor, dead.

Their spirits soared, their hopes were high,
A new era dawns, they thought with a sigh,
But power corrupts, and soon they find,
The pigs can become worse than humankind.

The slogan now, a bitter reminder,
Of a time when ideals were purer, kinder,
And the animals dreamt of a world anew,
Where equality and justice were finally true.

But now they see, with sorrow and despair,
That the pigs used them, that they don't care,
And the slogan that once inspired their fight,
Is now a painful echo of their lost light.

Four legs good, two legs bad,
A powerful slogan, now lost and sad,
The animals mourn, their dreams shattered,
Their hopes for a better world, battered.

Now four legs are good, but two legs are better
The animals have much less than they had before
They work harder, more, they have lost the fight
And their new masters, the pigs, now walk upright.
why who