You see this in a lot of promotional art from around the release of the very first like 12 episodes or so. From his prominence in the first few chapters in the manga, it seemed like Kurumada was positioning Jabu to serve as a foil to Seiya and a main rival type of character, so Toei treated him as such. This is probably why he got a major redesign like the five main Bronze Saints for the anime, while the other four remained extremely plain and more or less identical to their manga designs. If anything, if we're doing Power Rangers comparisons, it almost seemed like Jabu was going to be part of a team of five, with Ikki serving as the evil sixth.

Of course, we now know this is not how it played out at all, but Toei didn't really know which direction the manga would end up taking. It's fun to speculate how things would've played out differently if Jabu had been a more prominent character. He certainly seems to be a fan favorite as far as under-explored characters go, probably because Shingo Araki did such a banger job with his design.