Why can some clients not just say what they want?

I spoke to a potential concert photography client who was pretty keen because somebody gave me a good reference. They didn't put up much of a fight and just asked to write a proposal (they're a big organisation so they need a formal document with prices and such) and it will probably get approved.

They then rejected the proposal via text telling me they "want more of a wedding/event photographer package wherein you do candid shots the whole day." They did not mention this at all. I did ask during our first chat what they wanted and they said "oh we're quite flexible."

Is this normal? I'm new to doing paid work but am I meant to read my client's mind like we've been tepidly married for 20 years?