Is this strange behaviour from this man?

Was dating a guy who ended things early this year as he didn’t feel romantic. He seemed a bit avoidant in some ways. Was surprised ended things as we were really connecting and also had a good physical connection

He stayed friends. Asked to see me In April and he was hugging me and telling me how great I am and how he loves seeing me and how well we get along.

In may he texted me asking about my holiday. I replied telling him all about it and asked him how he was doing. He never replied.

Then the other day he replied to my Instagram story ‘hope you are well.’ I thought he wanted to open up a conversation so I replied and asked him how his new job was going.

Once again…. Silence. He didn’t reply. And I’m sat feeling sad and worried what’s wrong with me.

Why would a man message you first and then never reply?