imparfait vs passe compose

There is not just one specific use case for imparfait, or passé composé. It is common to use imparfait and passé composé like this - imparfait referring to a background action, passé composé to an event that occurred within the time period of the ‘imperfect’ one. Something being progressive doesn’t preclude passé composé - there is still an implicit time period here. Try this external link -  noting that it the use of the tenses is not ‘absolute’ but bidirectional - certain situations will generally be described by imparfait or passé composé, but in other situations the use of imparfait or passé composé defines what is being described. https://www.frenchtoday.com/blog/french-verb-conjugation/passe-compose-versus-imparfait/