An ancient prophecy foretold years before it happened.

In general, GT's entire goal seemed to want to combine OG Dragon Ball and Z. Mystical adventure mixed with sci-fi power fantasy. With tons of comedy and loud shouting thrown in.

But of course, then issues arose when they went a bit too far. Like de-aging Goku to make him the constant focus while making Pan and Trunks irrelevant. And most everyone will agree that Baby and the Shadow Dragons are neat ideas, but they were executed pretty poorly.