I can't understand the DOM behavior of list element

Why the ordered list DOM structure sometimes is ol > li and sometimes is ol > li > p?

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Can someone tell me the exact reason? I'm so confused about it. :face_with_spiral_eyes:

Ok, I finally found that when typing a list as usual, it is ul > li :

- item 1
- item 2
- item 3
- item 4
- item 5

But if I break it up into two, the whole list will become ul > li > p:

- item 1
- item 2
- item 3

- item 4
- item 5

I don't know if it's not a bug, but it made me confused when I've added some CSS styles to it and sometimes disappear.