Learn Spanish (Latin America): ¿Estaría animado el ambiente? Estaría repleto. - Was the atmosphere lively? It must have been packed.

This is a special use of the conditional tense to show probability or conjecture in the past. Instead of meaning "would be," it's used to make a guess, express doubt, or wonder about a past event. By asking ¿Estaría animado...?, the speaker is really asking "I wonder if it was lively?" or "Do you suppose it was lively?"

How does the second estaría translate to "must have been"?

When making a statement about the past using this "conditional of probability," you are expressing a strong guess or assumption. In English, we usually express this idea by saying "must have been" or "probably was." Therefore, Estaría repleto translates naturally to "It must have been packed."

Can estaría in this sentence still mean "would be"?

Grammatically, yes. Without context, Estaría repleto could just mean "It would be packed" (for example, "It would be packed if they lowered the ticket price"). However, Spanish speakers rely heavily on context. If they are discussing a party that happened last night, they instantly know the conditional is being used to guess about the past.

Why is the word order ¿Estaría animado el ambiente? instead of ¿Estaría el ambiente animado?