One of the most fascinating things about looking back at old anime and manga is seeing which franchises remain in the public consciousness and which get forgotten. Doubly so because this isn't directly correlated to popularity, as some shows that were despised or overlooked during their initial run grow into cult classics with constantly active fanbases, and franchises that were initially popular quickly vanish from the public's mind. No series fits the latter category more than Zatch Bell! Despite being loved, it's now hard to find in America. But the reason for this sudden vanishing is fascinating and gives a deep insight into the manga industry.
Source:https://www.cbr.com/what-happened-to-zatch-bell/