The __ of the king in running the country motivated the parliamentarians to usurp the throne & execute him; hence Oliver Cromwell was named Lord Protector of the realm.
The sentence came in fill in the blanks. The options are--
I chose "credulity" as the answer because a king can be dethroned by his parliamentarians when he is gullible, has blind faith, over trustfulness, unworldliness,lack of experience, ignorance etc. That's when the parliamentarians dare go against the king. N those are exactly what credulity mean.
On the other hand, complacency means self satisfaction, laziness and unwilling to work.
Comparing the meanings I feel it'll be credulity. Because a king can't be dethroned just because he is too self satisfied and lazy. This word doesn't mean the king isn't intelligent enough to handle the parliamentarians. But credulity does mean gullible and that is a great opportunity to dare go against the king. As the king is ignorant, synonym of credulity, so the parliamentarians wanted to take the opportunity.
PLEASE explain in details of whatever you think is correct. I'm having real troubles with the sentence.