Breakdown of Is deze man de overvaller? Ja, hij is het.
zijn
to be
hij
he / it (referring to a 'de'-word)
de man
the man
deze
this / these
Questions & Answers about Is deze man de overvaller? Ja, hij is het.
Why is there a het at the end of the sentence? In English we just say "Yes, he is."
In Dutch, you generally cannot leave the verb zijn (to be) hanging at the end of a sentence like you do in English. You have to point back to what the person is. Here, het acts as a placeholder (a resumptive pronoun) for the noun phrase de overvaller. Literally, the Dutch sentence says "Yes, he is it."
Since overvaller is a de-word, shouldn't we use hem or die instead of het to point back to it?
That is a great observation, but no! When replacing a predicate (the part of the sentence that describes the subject, usually after verbs like "to be"), Dutch always uses het. It doesn't matter if the word you are replacing is a de-word, a het-word, plural, or even an adjective. In this specific grammatical role, it is always het.
Could I just drop the het and answer with Ja, hij is de overvaller?
Yes, you absolutely can! Repeating the whole noun phrase is completely grammatically correct. However, using het is the most natural, native-sounding shortcut, exactly like how English speakers prefer the short "Yes, he is" over repeating "Yes, he is the robber."
Is overvaller the general word for a thief?