Complex sentence: The assassination attempt succeeded and Hipparchus was killed in 514/3, but Hippias remained in power and his tyrannical (by today's standards) actions in the remaining years of his reign are typically attributed by contemporary scholars as paranoia and anger over the assassination.
Split into simpler sentences: The assassination attempt succeeded and Hipparchus was killed in 514/3, but Hippias remained in power. The truly tyrannical (by today's standards) actions in the remaining years of his reign are typically attributed by contemporary scholars as paranoia and anger over the assassination.