Use of "whom" by NPR

Read this in an npr article and it felt off.

"In another civil case, Patriot Front was ordered to pay almost $2.76 million to an African American musician whom they assaulted in Boston in 2022."

Source: https://www.npr.org/2026/07/11/nx-s1-5888571/patriot-front-washington-dc

Always thought "whom" was used when the verb had a preposition.