Questions & Answers about To musiał być włamywacz, bo lokatora nie było w domu.
Does musiał here mean "had to" or "must have"?
It means "must have". In Polish, musieć in the past tense is used both for past obligation ("he had to be a burglar") and for logical deduction ("he must have been a burglar"). You rely entirely on context to tell them apart. Here, the second half of the sentence makes it clearly a deduction.
Why is the verb musiał masculine, when the sentence starts with the neuter pronoun To?
In the structure To + verb + noun (meaning "It was a [noun]" or "This was a [noun]"), the verb agrees in gender with the noun that follows it, not with the word To. Because włamywacz (burglar) is a masculine noun, the modal verb must take the masculine form musiał.
Why is włamywacz in the nominative case? Doesn't the verb być usually require the instrumental case for people?
Yes, but the pronoun To overrides that rule. Whenever you point someone out or identify them using To (like saying "It is..."), the noun stays in the nominative case. If the sentence had used a regular personal pronoun instead of To, you would use the instrumental: On musiał być włamywaczem.
Why is it lokatora nie było instead of lokator nie był?