Why __________ (Bill/sack) from his job? What did he do wrong?

Was Bill sacked is the correct answer because was Bill sacked expresses the simple past tense in the interrogative and in passive voice. It is the most appropriate answer as it gives the right tense and voice. The meaning of sacked here is dismissed. So, was Bill sacked means the Bill received an action i.e., terminated from the job.
Bill sacked is an incorrect answer because it is in active voice, and it means maybe Bill has sacked someone else and this action has no recipients. Thus, the use of Bill sacked has incomplete meaning in the sentence.
Is Bill sacked is an incorrect answer because it is in simple present tense and this tense defines an action that is happening on a daily basis, however, the action in the sentence states that it has already happened. So, the use of Is Bill sacked is grammatically incorrect.
Bill was sacked is an incorrect answer because it shows the declaration. Declaration is a formal announcement, and this is an opposite of the interrogative sentence and makes the sentence grammatically correct i.e. Why Bill was sacked (Bill/sack) from his job?