Is there anything in particular that stands out as being an obvious sign of a hoax?
For one thing it shows a classic "flying saucer" shape, and the whole "saucer" image comes from a misinterpretation of the Arnold UFO sighting back in the 1940s, so that immediately makes it suspicious IMHO.
Then there's the very unnatural and asymmetric wobbling motion. Ok you could argue that if it was an alien ship it might have an alien motion, but it just looks wrong.
I accept that those reasons are pretty subjective, but I also recall that there was analysis of the video which showed that while the buildings exhibited motion blur due to camera shake, the "UFO" did not (or at least did not to the same extent), suggesting that the UFO was not present in the scene as filmed.
I think the analysis was published in the MUFON journal but I don't have a link right now.