Psychopathology is more common than you might think. Research puts the incidence at about 1% in the U.S. *
Have you met 100 people? One of them is likely a psychopath.
Which, when you look at it objectively, is uncommon and far from the norm. The 99% (or maybe even more) would be the norm, not the 1% or less.
The other numbers you cite are what is thought to be true of the incarcerated which would not be applicable here, as the perp was clearly not incarcerated. And while higher, that portion is still only a small minority of the whole for those people as well, and therefore NOT to be the expectation of what we're looking at and what it looks like.
Frankly, I think you're working too hard to talk down or sidetrack the point that was made in the first place. The video does look like the actions of a thief, not an attacker preparing to attack a victim who will be arriving any minute. It is what it is.
If you want to ASSUME something else was happening, and base your thoughts on those assumptions, and try to make things fit to match, that's your right, but laying aside assumptions, I don't see any REAL question about what this looks like.
And that may not matter to you, but it sure alters my thinking to some degree. It has to.