Yup. My fan theory is that old testament god is the new testament devil.

Not necessarily.

For example, look at the story of Solomon's wise ruling.

It's an anecdote about how to tell between a true parent and a false parent.

In that story, the false parent is the one who only cares about being recognized as the parent and is willing to see the child suffer and die to achieve that result.

Whereas the true parent is the one who cares the most about the child living as their complete unadulterated self even if that means being entirely unknown to them at all.

The tradition of God as a divine parent in Judaism goes back well before Jesus, and the Solomon story sounds a bit absurd as an actual ruling.

But it's important to keep in mind that Solomon was a figure back in the polytheistic Israelite days which the version of the Old Testament we have today was actively rewriting the history of. So what was a poignant anecdote about the concept of the love of a true vs false parent dating from a period when Yahweh was married to the fertility mother goddess Asherah ends up just sort of randomly in there, surrounded by a bunch of claims about how Yahweh is a divine parent and if you don't acknowledge him as that he's going to smite you.

So it may have simply been changing it back to an earlier perspective. Potentially even informed by the above.

In fact, if you look extra-canonically, you can see Jesus saying:

Jesus said, "Whoever knows the father and the mother will be called the child of a whore."

(Solomon's story above related to the child of a prostitute.)