Maybe you should explain to him that you don't mind initiating contact so long as he doesn't purposely take too long to reply.

He may feel that he came off as a bit annoying, therefore waiting to see if you'd reply without him having to initiate conversing with you. Also, he probably waited an hour to respond because he probably didn't want to come off as clingy or needy.

Talk to him, and if this is the case and you don't feel that way, then reassure him that he's not coming off as clingy, annoying, or needy.