Remember that the bible traces the evolution of concepts of God, from the Bronze Age one among many to Biggest one among many, all through the Torah. Not till you get to the time of the Babylonian captivity, say around 500 BCE, is it thought that there are no other gods.
If you're interested in this evolution, you might find
>this article< helpful.
Then with Christianity, Paul decides to detribalize God and declares that the Jewish god is for everyone, and that the covenant of circumcision can be by-passed. If you read the covenant, you'll see that his argument is on the one hand specious in Jewish terms, but on the other, the reason why Christianity succeeded among pagans but in general not among Jews. Indeed by about 100 CE, direct antagonism between Jews and Christians can be detected in eg the gospel of John. And Christians have had an active antisemitic streak, with pogroms, deprivation of rights, ghettos, inquisitions and the Spanish inquisition, and so on, right through to the Holocaust, and even today.
Not till the 4th century CE does God become a Trinity. This idea is nowhere present in the bible, but is devised to solve the political dilemma, how to make Jesus, the principle object of Christian worship, into a god, while avoiding taunts, in particular from Jews, that Christians were polytheists like the pagans. The resulting Trinity doctrine not only doesn't make sense, but is said not to make sense, in that it's "a mystery in the strict sense", meaning that it "cannot be known by unaided reason apart from revelation, and cannot be demonstrated by reason after it has been revealed" (the churches' words, not mine).
In the meantime, the Christian God, starting in the 18th century and slowly developing the idea, became opposed to slavery, which is condoned both in the Tanakh and the NT, and from the latter half of the 20th century, particularly in the First World, has become more liberal on divorce, and at the present time is ceding ground on homosexuality.
A church that doesn't say what its parishioners think is right is going to lose parishioners, and that phenomenon, active in Europe from before WW2, is now making itself felt in the US, as articles with titles like "
the rise of the nones" will attest, though obviously other factors are at play too.