It was explained in the novel that in this timeline Cecil was actually influenced by the birds charm. Although Zeno is a high ranking spirit but he isn’t really strong with dark magic thats why Cecil was influenced by charm. In the current timeline Beritia has kuro(? Sorry forgot her name) which is a high ranking dark magic spirit which protected cecil.
It was explained in the novel that in this timeline Cecil was actually influenced by the birds charm. Although Zeno is a high ranking spirit but he isn’t really strong with dark magic thats why Cecil was influenced by charm.
In the current timeline Beritia has kuro(? Sorry forgot her name) which is a high ranking dark magic spirit which protected cecil.