Nowhere near fast enough. It's actually a perfectly ordinary flavor combination. There's no fundamental problem that needs to be explained.

It's just a meme. "Hawaiian" pizza was invented in the 1960s. It had the right combination of popularity and unfamiliarity to become a meme. Once it becomes a meme, it feeds on itself: people talk about it just because other people are talking about it, rather than because they actually care all that much.