But that assumes Stalin's goal was utopia. All the evidence I see is that his goal was power. By that standard, he did pretty well with the mass-murder philosophy and it was entirely rational. "Kill whomever opposes you or whom you suspect might oppose you" worked for Stalin for pretty much his whole adult life.
The same applies to many of today's liberals. They don't view their policies as failures, because the policies in fact achieve the real objectives. The only "failure" indicated by the policies' not meeting the claimed objectives was the failure of judgment of those who believed they would, or were even intended to.
That was his goal, but his followers, the ones that made his goal possible, believed that communism would create a Utopian society. They believed that the ends justified the means and still today millions of socialists continue to believe that the ends justify the means. Are they rational in believing that? Did communism and mass murder create a Utopian society? Will it ever?