At that point, most new Emperors were installed with the help of military allies, and it was not unusual for someone attempting to take the reigns of power to bump off the current Emperor. This did not result in very long life spans for most, with the exception of those few periods where the rule was relatively benign and some reforms were attempted.
Now, if you are knee-jerking, as I suspect you are, please hit the abuse button and have my previous post removed if you are so inclined.
I don't use the abuse button.