I think you are mixing stuff together in your post vs the title.
Hypnosis vids literally claim they can get you into a trance usually using different visual patterns, tones of voice & actual hypnotic techniques such as visualizing you dropping. I have watched a good deal of them & they have never put me in a trance BUT I have spoken with other subs who say they absolutely work on them, so I think its a combination of the particular video & your own susceptibility to them as well as any post-hypnotic suggestions given while you are on that state (if you get there).
On the other hand, I think what a lot of the videos you are talking about do is very Pavlovian & well established as succesful. Basically they associate a trigger with some activity by instructing you to give yourself sexual pleasure while watching and/or participating in it (cross-dressing or anal penetration as examples of the latter). Usually, these activities are the more extreme fetishes that you are actually not into until watching these videos over & over make this association in your mind. Which, in turn, makes then even more powerful as fetishes (even to the point that you can't get off to anything else).
As for recreational drug use being involved, that is pleasurable in itself. So, just like the sexual pleasure helping drive the new & powerful fetish... adding on another very pleasurable activity makes the trigger even stronger. The major downside is that fetishes are weird in that they can be so specific that that doing them in real life may be less than your video experiences because your partner can't hit those exact buttons (but if they do.. holy schnikies batman!
_________________________
Asp