How to get players to be curious and ask questions?

I have recently noticed that my players don’t really try to find out much about the world and story beyond the direct “what do we see?” I want to have them interact more with their environment and actually explore the reasons behind things without me leading them by the nose. “Why are these monsters working together?” “What are the villains trying to accomplish?” How do I get my players to be curious and ask those questions that start the gears of imagination like Who, What, Where, When, Why, and How?

These kinds of questions can really bring a world to life and add SO much depth to a story but they just don’t ask and if I tell them without them asking the game drags on and they begin to feel like I’m monologuing.