From his early years as Attorney General in the HW Bush administration, Bill Barr yearned for an opportunity to expand the powers of the presidency. He viewed the presidency as being the driving force of change in government and chafed at the limitations that had been put on it in the wake of Watergate and the Nixon resignation. How elated he must have been after biding his time for so many years, to again be appointed Attorney General, this time by Trump. At last he had an opportunity to put his ideas to work and to have a chance to make consequential changes to the balance of power for future presidents.
The bitter irony though, is that after waiting all those years, Barr got his opportunity with a president who was a honking, screaming, neon lit poster child for all the reasons why a president should not have greater power. Like a sea captain who wanted to show that ocean liners were the travel mode of the future and after patiently waiting for many years, finally got his wish when he was made captain of the Titanic, Barr's opportunity came with a fatal flaw.
Whatever fever dreams he and his fellow Republicans may have harbored over using that expanded power to say crush unions or left wing social movements or reverse the course of immigration in the country, instead the role Barr inherited, and for which he will be remembered, was not one of a champion of the far right but rather a sort of mafia consigliere, charged not with enabling grand visions but with the sordid and cheap activites of a fixer and enforcer,a glorified Michael Cohen, protecting Trump's corrupt friends from legal consequences and breaking the metaphorical knees of anyone he perceived as his enemy.
If he had become the Attorney General under a more typical Republican president and not the venal, corrupt Trump, he might have had a place of prominence in history at least among the far right. Instead, history will not be kind to him. He took his skills and zeal and squandered them for the most uninspiring of reasons, sinking into the swamp instead of rising above it. Future Attorney's General when confronted with a potential political scandal will invoke his name as someone you didn't want to emulate. Pundits will refer to any attempts to use the DOJ to perform the kind of acts normally associated with tin pot dictators, as attempts to "Barr-ify" the DOJ. He will be viewed in the same light as people like John Mitchell, the disgraced Attorney General under Nixon.
Of course, the folly of it all is that unlike the captain of the Titanic who could reasonably have expected things to turn out as he envisioned them, Barr had to have known before he took the job how bad Trump was and that things were not likely to end well. It's like the sea captain agreeing to command a rusted out hulk of ship which carried toxic waste instead of passengers as it's cargo,not a platform for changing the world but a fool's errand doomed from the start. How an otherwise smart person could make such a stupid decision is hard to fathom but like so many others in the Trump administration, he has traded in any future esteem for endless derision.