There seems to be a lot of confusion here. "It" is introduced in the English sentence because the Portuguese sentence doesn't have any pronoun. If it referred to a "he" or a "she" (and without any context to explain the sentence), the Portuguese sentence would have to start with "Ele" or "Ela" (ex: "Ele é como um maestro"). When I explain English to Portuguese translations I like to say that "it" doesn't mean anything in Portuguese, it is simply omitted from the sentence. So the English sentence with "it" seems accurate to me because the reverse translation works perfectly.
Notice that, given the right context, using "he" or "she" instead of "it" is also acceptable (i.e., if Duolingo finds it wrong you should report it). But the absence of context is a context by itself, and without context we try to see what's the most accurate interpretation of the sentence from all the available possibilities. Not only in Portuguese but in any other language.
The conductor might be a he/she, but the 'it' in this sentence isn't the conductor. It doesn't say 'It is a conductor' but 'It is LIKE a conductor' and something like a conductor could be an inanimate object, a robot/machine or computer as Tiago has suggested. It could also be a simile, again, as Tiago has suggested previously.
Perhaps I should have explained better. In a literal sense, yes, it has to be a person. But the sentence is a simile, so when you say "It is like a conductor", you could be referring to something else: maybe a computer, like in: "This computer controls these 50 machines in perfect synchrony. It's like a conductor"