Old Major's political philosophy of Animalism is expressly designed to liberate the farm animals, to free them from the oppressive yoke of Mr. Jones and other humans. In the Animalist utopia envisaged by Old Major, all the animals will come together to create a world of peace and plenty, where animals will finally be treated with the dignity and respect that they deserve.
Sadly, things don't turn out like that. As is often the case with projected utopias, Old Major's ends up as a brutal tyranny in which starvation, terror, and fear are very much the norm.
The road to hell is paved with good intentions, as they say. And while there's no doubting the goodness of Old Major's intentions, it's also impossible to overlook the hell to which those intentions have led. The Animalist revolution was supposed to liberate the animals. In actual fact, it's led to an even greater enslavement than they endured under Mr. Jones.
Animal Farm is, of course, a satire on the Soviet Union under Stalin. The communist ideology espoused by Lenin—on whom Old Major is based—was doubtless full of good intentions. Communist ideology was based on the notion that a better world was possible for the poor and the downtrodden and that once they'd taken power for themselves, they would be able to construct a workers' paradise.
But as with the farm in Orwell's story, the Soviet Union under communism became a veritable hell for those that the revolution was supposed to serve, with famine, repression, and terror becoming the norm. In both the farm depicted in the story and the country on which it is based, the road to hell was paved with the very best of intentions.