By all reasonable accounts, GW Bush should have been prosecuted for war crimes. Trump should have been prosecuted the moment he left office for a spectrum of crimes. There is even a strong argument that Obama should have been prosecuted for drone strikes on citizen combatants.
But power protects power, and the moment that seal is broken all hell breaks loose amongst the ruling class.
How many people were held accountable for the 2008 crash? Zero. That would mean everyone else has to stop their criming too.
Who knows, maybe Trump is stupid and petty enough to take revenge on his enemies. If he does, no doubt his entire administration is the next against the wall as soon as the winds change.