Okay, maybe Calvinism doesn’t lead to universalism inexorably–as if every Calvinist must become a universalist. However, many leading universalist theologians are/were Reformed and believed that their Calvinist concepts of God’s sovereignty eventually compelled them to embrace universalism.
Two notable examples come to mind: Friedrich Schleiermacher and Karl Barth. Yes, I know some Reformed people will reject one or both of them–as not truly Reformed. However, one cannot read Schleiermacher’s The Christian Faith and miss his strong Calvinist principles. For Schleiermacher God is the all-determining reality and that is why he rejects petitionary prayer–because it implies God does not already know what is best. For Schleiermacher, whatever is happening, including sin and evil, are foreordained and rendered certain by God.
Schleiermacher embraced universalism because he could not reconcile the all determining God of Jesus Christ with hell. If God is love and all-determining we must conclude that there is a loving purpose for everything that happens. If God is the author of sin and evil, then eternal punishment of sinners in hell is unjust. Schleiermacher the Calvinist saw the issue clearly and drew the only logical conclusion from his high view of God’s love and sovereignty.
For all his differences from Schleiermacher, Karl Barth followed the same basic path from Calvinism to universalism. I know some Barth scholarly do not believe he was a universalist and he did not embrace that label. But I believe universalism is implied in his doctrine of election in which Jesus is said to be the only reprobate man. Barth famously declared that our “no” to God cannot stand up to God’s “yes” to us in Jesus Christ. For Barth, God is “He who loves in freedom.” God is also all-determining in his sovereignty. Barth called his soteriology “purified supralapsarianism”–purified of hell but nevertheless supralapsarian! Barth saw rightly that the inner logic of Calvinism must lead to unversalism IF it takes seriously love as God’s nature.
The only way for a Calvinist to avoid universalism is to make God a moral monster who condemns people he could save to hell for his own glory. Once you see, however, that hell is totally unnecessary because the cross was a sufficient revelation of God’s justice, hell becomes not only superfluous but utterly unjust.
I have sometimes said that IF I could be a universalist I could be a Calvinist. Well, I would still have the problem of human responsibility. But my point is that I don’t care about free will except insofar as it is necessary to explain why a God of love allows some people to perish eternally. If I could believe that God saves everyone unconditionally, which is what I think Barth believed, I could be a Calvinist. One reason I cannot be a Calvinist is because being one would require me to jettison all the biblical material about hell because I would find no point in even being a Christian if the God of Christianity were a moral monster.