Explanation: Antoninus Pius is one of the longer-reigning Emperors of the Roman Empire. Why does no one remember him? Because he did nothing.

Not literally nothing, but his reign contained little in the way of excitement. No great invasions or defenses, no fundamental reforms in yet another misguided attempt at adulation or military glory, no crisis that was allowed to blossom to such a stage. Just a quiet, diligent man who was noted to enjoy fishing in his down time, keeping a steady hand on the tiller of state. When his ~23 year reign was over, letting the gears of government turn with nothing more than addressing problems and clarifying legal issues as they arose, the Empire looked much as it had when he had inherited it - just with a bit more of everything - charitable organizations, completed infrastructure projects, legal protections, slave rights (but still slavery, because the past is a shitty place), money in the treasury...

Antoninus Pius did nothing, actively. By inaction, he chose the best possible course of action in his reign. o7

Wu wei is a Taoist concept Romans were unlikely to have been aware of.