I feel intrigued, this Randic Torn is mentioned in Redguard lore a commoner who took over government after the military dictator Mensel Sesnit, and then he ruled Yokuda (I assume he ruled Yokuda since the redguards still hadn't arrived in Tamriel at the time) for 120 years.

Now, how come a commoner came to this position and how was he able to live that long?

There's no indication of a military uprising by Randic after Sesnit's assassination, so Randic Torn may well have been a high-ranking commoner military officer or bureaucrat that was either Sesnit's formal successor or simply the man most capable of reining in the State.

As for how he lived that long, magic.