Or HaChaim on Exodus 32:35/אור החיים על שמות ל״ב:ל״ה

1 אשר עשה אהרן which Aaron had made. What was the Torah's purpose in making this statement at this point? Perhaps G'd wanted us to know that the Israelites were punished for causing Aaron to become the innocent maker of the golden calf. G'd deals severely with anyone who causes a great and holy man such as Aaron to become involved in the performance of a sin.

2Alternatively, the Torah wanted to ward off any accusation anyone had levelled against Aaron who was only technically the maker of the golden calf, and to place the blame where it belonged. The fact that G'd smote the people for a calf which Aaron had made, is evidence that G'd considered the people as having made the calf.