A hoaxer is much more likely to cut the rope. Why? Odds are, such a person would probably be far less likely to know how to tie a "noose" knot. So cutting a "pre-made" one is the quickest way to the hoax.
An actual racist hater who thinks about "nooses" and be predisposed to something like this, would much more likely know how to tie one, take the few minutes to tie one.
Now of course we know they were all idiots, and the rope wasn’t actually cut when it was found, it was cut later, and the ‘finder’ actually believed someone had tied a noose into their garage door rope-pull, AND NASCAR went along with it, instead of starting with “hey, lets not jump to conclusions, let’s see if this was just a loop.”
Note: whoever made the loop for that door DID make it a noose; something I might have done when I was younger, although nowadays I think I’d be smart enough to be scared of getting cancelled , and use a simpler knot.