Were the First Monotheists Really Monotheistic?

The title is an odd question, I know, but it's worth asking. The Hebrew Bible is full of lines that suggest that the Israelites were being cajoled and threatened into choosing Yahweh from among multiple possible alternatives. According to My Jewish Learning, the second commandment states in Exodus 20:3-6 is "You shall have no other gods beside Me.... You shall not bow down to [graven images], nor serve them, for I, the Lord Your God, am a jealous God, visiting the iniquity of the fathers upon the children unto the third and fourth generation."

Does this sound like a deity claiming to be the one and only? I don't think so. It sounds more like a claim against other deities. And who could Yahweh be jealous of? This sort of idea can be found throughout what is known in Judaism as the Five Books of Moses. 

In Exodus 6:6-8, we "hear" Yahweh telling Moses, "I will take you [Israelites] as my own people, and I will be your God." Why wouldn't The One and Only God present himself to all people? This just makes no sense unless each people was expected to choose its own god.

Of course one can find lines in the Five Books that sound monotheistic, and a key Jewish prayer does indeed state, "The Lord our God, the Lord is one." But even that could be interpreted to mean that the Israelites have only one Lord. It doesn't rule out other gods for other people. Those words, which constitute what is called The Shema, are found in Deuteronomy 6:4, which was apparently written later than the other four books. But even the full Shema introduces doubt about monotheism, for Deuteronomy 11:16 states, "Take heed to yourselves, lest your heart be deceived, and ye turn aside, and serve other gods, and worship them." Other gods--that sounds like a reference to actual rivals for the Israelites'  attention Yahweh rather than to manmade gods. By the way, in the previous verse, Yahweh engages in bribery, promising rain for the land and grass for the fields in return for worship and obedience. 

We also have it on good authority from modern archaeologists that the Israelites--who were Canaanites, not outsiders, despite what the Bible says--worshiped multiple Gods. The Bible says that ambitious kings of ancient Israel and Judah occasionally disciplined wayward members of the 12 tribes by smashing their "high places," which were altars on which animals were sacrificed to gods other than Yahweh, who had to be worshiped in the temple of Jerusalem.

We may reasonably suppose that up until late BCE, the Israelites, or Hebrews, were not strict monotheists. Instead they were henotheists, that is, worshipers in a tribe or family of one particular god out of several, and perhaps practitioners of monolatry, who favored of one deity over many. The implication is that henotheism is more tolerant than monolatry of other people worshiping other gods. "To each its own god" rather than "my god is better than your god." We also have indications that many Hebrews combined worship of Yahweh with worship of other tribes' gods. In a word, they were polytheists.

The Israelites, known as Judeans, seem not to have become monotheists until the Hasmonean (Maccabee) dynasty, sometimes at swordpoint.