This is how I’d explain it. More specifically this is an example of a concept called a “dummy pronoun” in English. Phrases like “it is clear that…” Or “it is raining” are using “it” as a dummy pronoun. They’re used to express a verb without expressing a subject. in other words, [verb] is happening.

https://en.m.wikipedia.org/wiki/Dummy_pronoun

I feel the pause of the Oxford comma when I speak. Always throws off the rhythm of a sentence when I don’t see it in text.