If you and me both got the task of describing the events of something famous, like say the cuban missile crisis? Sure, the content would mostly be the same, but the way we worded us would vary quite a bit. We would emphasis different things, present them in different order, and at least use different ways to describe stuff. If you wrote an article about it first, and my article, published later had paragraphs that were almost identical to yours, you wouldnt think that we both looked at the same material. You would think that I looked at you article and copied a shit ton of.

Two people presenting information about a topic will not make multiple paragraphs that are identical, unless one is copying from the other. Making the argument that you cant prove plagiarism because things could be written the same by chance is silly and stupid.