It seems the FIB was too busy trying to prosecute political crimes to be bothered with real crimes.
The FBI has much more important things to do.
https://www.foxnews.com/media/minnesota-high-school-student-falsely-accused-racist-messages-hoax
MN teen falsely accused of sending classmate racist messages: ‘I felt unsafe in my community’
The so-called racist messages were discovered to be a “hoax” after White Bear Lake High School, the FBI, and the local police department investigated the situation.