(In my theory) Raddy tried to fight Simonos but Raddy lost and If you look closely, Raddy neck didnt got snapped and didnt made him die instantly. Instead, Simon slashed or ate a piece of Raddy neck, making Raddy bleeds for minutes, Simon let him agonize and leave, As you can see Raddy's expression hes full of pain and agonization and hes choking with his own blood and then died