Young native-speaking males emphasizing deep voices
Solution 1:
What I hear in your video is vocal fry, the somewhat raspy sound in a very low tonal register.
It is a semi-voluntary affectation (this sound can also be the result of a a speech defect, but that is usually not the case). It is generally found to be more common among women than among men. It has become 'popular' among younger speakers in America fairly recently, that is, over the past fifteen or twenty years or so. The Wikipaedia page has some theories about it, but there is lots more to be found in linguistic research papers.