@Jim40 Inquiries are just that- a way for guests to ask questions without committing to a booking. Some may not even be that serious or have their flights booked or anything- they're just scouting the possibilities. They may have sent out Inquiries to 5 different places, as far as you know.
It's frustrating when a host takes the time to message back and forth and then the prospective guest just drops out with no explanation, but it's part of hosting. The nice polite ones will message you back, thanking you for your time, but most (aside from the ones who go ahead and book) you never hear from again.