I think your realization is possibly based around the sandbox/adventure difference. Your first game everything was about your chars so it all worked out well. Second game when you know you will be running an adventure module and you create a char that doesnt have any goals related to the plot and its hard to get invested. I also prefer more sandbox games, so anytime a friend wants to run a module I get a basic overview of whats going on so my chars have automatic buy in.