чем занимались

what were you doing?

→ что
phrase Rare #47,467
what were you doing? The subject is often omitted and understood from context; the plural past form can refer to «you» or «they».
RU: Чем занимались вчера вечером?
EN: What were you doing yesterday evening?

Чем занимались?

What were you doing?

А чем занимались профессора?

And what did the professors do?

Чем занимались после ужина?

What did you do after dinner?

Вам известно, чем занимались вы и другие.

You know what you and the others were doing.

— Последний император (1987)