Seems from the English script that it is because it is 1. “in order to make us” - afin de/pour nous faire - and the action that is being caused to be done is 2. “ do our homework”  - faire nos devoirs. Hence it becomes ‘afin de/pour nous faire faire nos devoirs’ as a causative statement.  Faire + [infinitive] = to have something done in French (Causative)

https://www.lawlessfrench.com/grammar/faire-causative/