Why was commodus assassinated?

Commodus was murdered on New Year's Eve of 192. Because he had not chosen a successor, civil war broke out and in five months four emperors were to rule Rome. Commodus was followed by the virtuous Pertinax, who ran an honest government, reduced spending, lowered taxes and even found homes for Commodus' 600 concubines.

hi, according to my research the answer to the first question would be false. al tabari was the author of the first medical encyclopedia & he was a persian scholar not arab