Jason Pelletier couldn't sue the true cause of the crash, Brandon Berman, since he died.
Odds are, Berman committed a somewhat complicated suicide as he probably wasn't sitting back in his seat, with he seatbelt fastened, as was deliberately distracting the driver.
Pelletier, as a fellow passenger, had a personal responsibility to ensure his own safety, and should have been acting to stop Berman.
Maybe he was. There's a decided lack of details.