A. As for why, Peachey's reason is good!

The theater performance was a success. < Correct. It happened and it was successful. The theater performance succeed because _________________ . and why? < don't know why you used this. Just put the reason for the success at the end of the sentence.

Really? OK, here's a hint: The verb "succeed" is present simple, but not conjugated for 3rd person ("it").