The object of a verb is usually marked with を, but when that object is the topic of the sentence, を will be replaced with は. This is a basic grammatical rule, and it has nothing to do with the usage of 通して itself. See: What is a topic prominent language?
In your example, みなさんのパフォーマンス is the topic of the sentence, so it's marked with は even though it's the object of 聞く.
EDIT: Note that the object of みなさんのパフォーマンス is 聞く, not 通す. 通して is the te-form of 通す, and here it's working like an adverb that describes how the main action (聞く) is done. Compare: 音楽を座って聞く ("to listen to the music while sitting"), リンゴを急いで食べる ("to eat an apple in a hurry").