It is more likely the ratings fell below a level thought acceptable by the advertising paymasters, so the show was canned.
It happened to Kenshin, which was still receiving an 8% audience share (8% of the viewing population) when it was cancelled. Most shows are lucky to get that. Then again, Kenshin was on during primetime. Most shows are on some time past midnight.
Comparitively speaking: Sazae-san, the highest rating anime, gets around 17-25% audience share. It is also cheap, family-friendly and poorly made pap.