Sounds like this spread through meme soundboards and short video edits where a short, repeatable taunt can be reused in almost any context. The loser you're a loser phrasing became popular because it needs no setup or explanation, and its looping delivery makes it easy to time to a facial reaction or a scoreboard. It is now used alongside other reaction clips such as the emotional damage meme for exaggerated roasts, keeping it in circulation as a go-to joke for losses, fails and friendly teasing online.