Hen nan is Mandarin for very difficult, and the two-character phrase is widely recognised by Mandarin speakers as a blunt way to say something is too hard. Online, short reaction clips like this travel easily because they need no translation for viewers who already know the phrase, while subtitles or context help everyone else catch the joke. It fits the short-form habit of answering a frustrating moment with a single line instead of a long explanation, which is why it keeps appearing in gaming clips, study videos and everyday fail compilations.