No one explicitly said Zantabraxus herself tried to do something.
It's very likely that the mess with local temple politics including a coup and counter-coup was too big to just evaporate the moment Zantabraxus retakes her throne.
Could be a bunch of priestesses (possibly, but not necessarily from Team Eshkigax) or someone high-ranked working with them. Who could intentionally misrepresent their authorization, or maybe Klaus simply jumped to a conclusion.