“What’s (all) the fuss about?”： Why everyone was excited; why it’s popular, The speaker literally wants to know what the agitation is about. （这到是什么情况？）
中文释义：提问者想要了解：是什么情况让人们异常兴奋或躁动不安、聚众集会，或发现一种事物的流行，要想探个究竟。类似的表达：why (all) the fuss？，两者之间存在一点的差别，详见：
“Why the fuss?” The speaker knows what the fuss is about and thinks that it is insignificant, not worth bothering about. A rhetorical question.
“What’s the fuss about?” The speaker literally wants to know what the agitation is about.
This is much the same difference as asking why something happened versus asking what happened.