As a long time follower of the Mahon/Flood Tribunal my main take away is this (and no doubt Public Inquiry thinks similar):
Throughout that period, corruption in Irish political life was both endemic and systemic. It affected every level of Government from some holders of top ministerial offices to some local councillors and its existence was widely known and widely tolerated. Although that corruption was occasionally the subject of investigation or adverse comment, those involved operated with a justified sense of impunity and invincibility. There was little appetite on the part of the State’s political or investigative authorities to take the steps necessary to combat it effectively or to sanction those involved.
All I would add is this: Nothing has changed.