The phrase I totally hear you has long been used in everyday conversation as a polite but pointed way of saying that someone is not really convinced, and that familiar social meaning is exactly why the clip works online. Short reaction sounds like this spread through meme edits, reaction videos and short-form posts, where a few seconds of speech can replace a whole caption. Creators keep returning to it because it is instantly understood, easy to drop into almost any argument or storytime, and funny precisely because the agreement sounds so unconvincing.