You have the basic data correct. You're just missing the Jewish history regarding how this fits together. But you aren't wrong exactly as some suggest.
In short, my people, the Hebrews, are likely the people of Canaan. Yes, we're the very same people that the Tanakh (or Hebrew Scriptures) claims were conquered and overtaken by the Jews. What the Biblical narrative describes is the way our culture rewrote its history while they were captives in Babylonian exile. Without nation and without shrine or temple, the Jewish people could have simply assimilated like most cultures do that are captured. To prevent this, they took various stories, tales, narratives, and a little bit of history, and wove it into the stuff of legends. The various names of God come from this redaction while in Babylon.
"Paul Revere's Ride" by Henry Wadsworth Longfellow (most often referred to as The Midnight Ride of Paul Revere) is of the same type of genre. Longfellow's famous poem is read in America as history, with Revere seen as the hero who warned the colonists: "The British are coming! The British are coming!" In reality, Revere was not the hero of this historic event. The events described by Longfellow were accomplished by a group of colonists, among whom Revere was merely included. Paul Revere, however, did not accomplish what the famous story states. Revere was captured by the British before he could warn anyone, and thus he never turned out to be the hero the poem details. The actual person who warned of the British invasion was Samuel Prescott, not Paul Revere.
However, Longfellow's poetic license made the historical event easy to remember and be taught to school children. It also encompases the lessons of values treasured by the newborn nation and its hopes for its own future. He wasn't interested in teaching history as much as passing on the values of America to future generations. The story in the Hebrew Bible is the same type of narrative.
When the exiled Jews living in Babylon turned their history into legend like Longfellow, they used the various names of their concept of "God" that had been adopted through the ages. The people of the Fertile Crescent that came to be known as Canaanites were likely among the people who migrated to Egypt when it was ruled by the Hyksos, a foreign power. When the Egyptians regained control they attempted to make slaves of the various peoples who had moved into their land. These migrants escaped and returned home, for some this meant the Fertile Crescent or land of Canaan. When the Davidic dynasty took control centuries later, it made the worship of the one God YHVH the state religion (or at least attempted to). Eventually the kingdom of Judah got swallowed by intrigue with the Babylonians that led to their exile. At each of these various points, the concept of the Hebrew God was different as were the names applied to God.
In other words the differing "names" of the Jewish God-concept in the Scriptures are those that were picked up by the Hebrews along the way during the march of history. "El" was the name of the deities of Canaan, for example. "YHVH" was the name of the deity worshipped by the Midianites or Sinai people the Hebrews met as they left Egypt. And so forth, and so on. The various names and titles you read in the Scriptures come from these different eras, and you can often trace how old a story is in Scripture by what name they use for God.
This is what led to the creation of the Document Hypothesis, the idea that the Torah is a patchwork of redactors. These different names for God and the different ways the name of God and the concept of God is handled throughout the Torah, for instance, helps one decipher when the portion or narrative originates in history. This has helped not just scholars but the Jews themselves understand how to apply the laws of Torah, whether something was literal or whether something was merely allegorical.
So what you are seeing is not a careless cover-up but earmarks of the origins of stories that were woven together into what we now have. It also shows something different about how Jews see God than what you might be familiar with. Unlike what Christians believe, Jews didn't just suddenly come to worship YHVH in one, sudden swoop of heavenly revelation. It took generations, many, many centuries for the monotheism of Judaism to develop. A lot of the practices and concepts of the theology comes from the paganism of the earliest days of my people. All of these details were given a new meaning once the theology had evolved into what it was when the Jews were in Babylon. They shoved it all together while in Babylon and began creating what you know today as "The Bible."
Contrary to the Christian concept, the Jews don't see their view of God as one that has ever been static. As the "children of Israel" (Israel meaning "one who wrestles with God"), the Jews have wrestled with their God-concept over their own history. It has evolved as they as a people have evolved. In contrast, Christians see the revelation of God as something static and unchanging. The idea that celebrations like the Passover and the various names of God having pagan origins is unacceptable to them, but we Jews have always known our own roots.
And the Jewish concepts about God have evolved even further in Judaism. For instance, today most Jews acknowledge God as undeniably real but at the same time they don't "believe" in God. While this may seem impossible from the narrow static view of Christianity, it just demonstrates how the ideas you are talking about are somewhat passé in the culture that produced the Bible. We have moved on, preserving and learning from our past, but using this to evolve into the future. Christians, on the other hand, stare at the past and try to nail the present to fit into that mold.
It is this Christian view that has caused you to be surprised by this information. If you had asked a Jew years ago in the first place, you would never have found any of this data as surprising or challenging.
