I don’t think that the Old Testament God ever was a universalist one, appealing to all the earth’s peoples. AFAIK, He only manifested Himself to His Chosen People (the Hebrews/Israelites), and never cultivated any relationship with any other group. Virtually the only mentions the other ethnic groups (the Philistines, Canaanites, Ammonites, Hittites, Shumanites, Egyptians, etc.) get in the OT are in the context of their conflict with the Israelites and, depending on whether the latter has been sufficiently worshipful of God, how God ends up rewarding or punishing His Chosen People on the battlefield.
I hardly know what’s worse: to be God’s favorites, and so be held to a different and higher standard of conduct and absolute obedience to His dictates and whims, however arbitrary or even silly they may be (actually, to be held to any standard at all; God didn’t communicate with the heathens, period), or to be used as God’s tool of retribution to punish Hebraic irreverence, via a military defeat, enslavement, political subjugation and heavy taxation, or what have you.
So if God’s the Father of all humankind, He’s a parent of extremely questionable wisdom and fairness, playing overt favorites like that, urging his children to fight and kill each other, and letting the outcome be determined by how slavishly appreciative his favorite kid has been acting. I mean, if this religion isn’t a thinly veiled metaphor of the state of human relations and government at the time, with all its brute force, authoritarianism, and ignorance, I don’t know what is.
Now it’s true that Jesus preached a universalist message and that the religion which emerged in the name of an honorific of sorts imputed to him has always stressed conversions and witnessing his message to the peoples of the world and so forth – but even this evangelism, so at odds with the Judaic traditions that Christianity emerged from, occurred with a rabbi as its messiah active first and foremost in the Jewish community. It’s not as if Jesus travelled the Marco Polo route and then some, reaching more of the peoples of the world. Better yet, if God really wanted to spread a new universalist message to everyone, why rely on a single prophet (who by circumstance was only going to reach and appeal to a small number of people)? Why not emblazon the new message in the skies for everyone to see and read it in a loud booming voice for the benefit of the 98% [or thereabouts] of the population which was illiterate?