The Reason Zenos.

[Bongaboi]

I got a feeling we're going to silence Elidibus soon. Zephiroth-er, Zenos will be later.

[Gemina]

No, he won because the fight was designed in a way that you cannot win. I think you're looking too far into gameplay vs lore. All you need to know is that at the start of SB, the Wol is outmatched by Zenos, but throughout the course of SB the Wol becomes strong enough to stand toe to toe with him, creating the current rivalry between them.

If you want to look at it like the only difference between the start of 4.0 and the end of it is 10 levels and gear, that's fine. But the Wol and now Zenos continue to get more powerful with each patch that comes out.

[Mansion]

(And on that power scaling topic, there's still the fact that while we are very efficient to kick some Primal/Sin Eater, against another kind of enemy we aren't that overpowered. We saw that with Ranjit for instance. In the lore, we sometimes do need some power up phases based on whatever we are conveniently doing at that time so we can take on a mighty enemy).
(But I do think sometimes it's not doing any good to try to link too much lore and gameplay)