These poops are unabashedly immature edits of other videos. By using extremely simple video editing techniques, such as cuts, loops, flip screen, magnify, zoom, mirrorimage, sound effects, rewind, suddenly loud as fuck, etc. one can "poop" a video (usually already funny without poopage) to take words and situations out of context, make in-referencing to other poops, and generally make complete lack of structure hilarious. If you don't find this funny, fuck you.
durhamrockerz is my favorite youtubepooper, and convinced me that the youtubepoop genre wasn't just hit or miss funny, but can be very strategically funny indeed.
Happy in Paraguay, not really a poop, but the last few seconds in the ending are straight poopage.
I believe their ancestry can be traced back to the animutations and fanimutations that followed thereafter so many years ago on albinoblacksheep. in the same way, they are only funny to people who spend too much time on the internet.