NHTSA formally investigated Tesla Autopilot after incidents in 2016, 2017 and 2018. There was also a formal NHTSA investigation into Tesla battery fires in 2013. These investigations span 3 presidencies under both parties.
NTHSA also is the type of agency that got lobbied by auto makers into instituting the minimum 25 year old import rule under the pretense of safety, because it ate into profits of foreign manufactures selling cars in US.
