The phrase itself is everyday Mandarin, formed from ke shi meaning but or however and ta meaning he, so the clip carries no finished statement of its own. Its popularity online comes from that incompleteness, which lets editors attach it to almost any scene where someone hesitates, objects, or tries to pass responsibility to another person. Short voice fragments like this circulate through soundboards and short video edits, where a fraction of a second is enough to signal a rebuttal without needing any further dialogue or explanation at all.