Simplify the following text for a Grade 12 native English-speaking person.
Original: The city was left very skeptical when Vitellius chose the anniversary of the Battle of the Allia ( in 390 BC ) , a day of bad auspices according to Roman superstition , to accede to the office of Pontifex Maximus .
Simplified: The city was left very skeptical when Vitellius chose a day of bad auspices ( according to Roman superstition ) to accept the office of Pontifex Maximus .