The writing has something to do with it. Not that it's bad but it doesn't have well defined arcs which makes it less marketable. I feel like at one point the story must have been heading for a definitive ending and then the plan changed.
The "Chronos Japan" arc is very brief in the manga. Then almost too much happens in the Mount Minikami story line. One right after the other we are introduced to Lost Numbers, Hyper Zoanoids, a proto-zoalord, a true Zoalord, and then the original Zoalord.
The lore introduced is really cool but limits where the series can go. We know all about th