Explanation: The Emperor Vespasian came to power after a civil war, the first of the Principate, and was very careful to formally respect the power of the Senate (though he was not entirely above abusing his autocratic power, exiling and eventually executing one of his most recalcitrant enemies in the Senate). He died of natural causes. Vespasian's favorite son and heir, Titus, went even further, and, during his reign as Emperor, abused no Senators and always treated them with the utmost respect.
Vespasian's second son, Domitian, who came to power after Titus died suddenly either of illness or of poison, gleefully flaunted his power, executing dozens of Senators, insisting on being called "God and Master", demanded unearned titulature honors, regularly threatened Senators for the fun of it, and had the gall after all of that to whinge about how horrible it was to have to fear for his life as Emperor.
Domitian was eventually assassinated with the cooperation of his own household.