7 years since my last credit card closed. It was always paid in full by the due date and I think I had about a 15K limit on it, but it was just easier for me to handle stuff in other ways.
That’s why it dropped. You use too little credit (according to the bureaus, not me) and that account, once it dropped off your report (which all accounts do after 7 years) there was less to “go on” for a score.