Am I missing something, or is modern dating really like this?

My brain genuinely can’t understand this. How can someone who was messaging me every day suddenly stop replying? We haven’t met in person yet, but we had talked about going on a date once I’m back in town. He seemed interested and was waiting for me to return. Last night we talked a little bit. I sent him a landscape photo I took because he likes photography, wished him a good night, and since then… nothing. What confuses me is not even the possibility that he lost interest. It’s that if I were in his position, even if I no longer wanted to meet someone, I’d still send a polite message explaining it instead of disappearing.
Is this normal? How do people go from actively talking and making plans to complete silence so quickly?

I’m also just exhausted because I keep running into this in Berlin. Active conversations, plans, interest… and then suddenly silence. I cannot comperehend.