It comes from the mediocre-read who cannot be satisfied with the available vocabulary and decide to borrow vocabulary that has only tangential connection. In this case, "tremendous" has a tangential connection through the sense of huge magnitude. People also don't listen to what they are saying. When someone exclaims about a social event, "it was the Bomb!" do they realize they are glorifying a mass murder phenomenon?

So, it is not that words meaning "bad" are being used to mean "good." It is that people are stupidly misusing words.