Trump would never shut down the DOJ. It's too important a tool he needs to support his lawlessness should he ever get re-elected.
Keep in mind that even Russia has a Constitution, a system of courts, lawyers, parliament and punishment for wrong doers, etc. Putin didn't abolish anything. He filled his government with bobble-heads and oligarchs just like Trump wants to do. It's how he holds onto power and why Putin can AND DOES murder his opposition with impunity.
Trump started to copy cat Russia when he became president. He put people, like Bill Barr for example, into a position that Trump needed to protect himself from incrimination. He appointed cabinet members to start tearing down the State Department, the CIA, the Intelligence community, the EPA, Homeland Security, the Department of Education, the Treasury Department, the U.S. Postal Service, etc. Then Trump began to create his own wealthy oligarchs, all indebted to him to him, (just like Vladimir Putin) by increasing their wealth with tax breaks and thus earning their willingness to assist him with anonymous donations to PACs set up for that very purpose.
For four years Trump went on a spree to spread lies and propaganda throughout the country to cause dissention, mistrust and turn us all against each other. Democrats against Republicans, neighbors against neighbors, blacks against whites, the South against the North, Americans against immigrants, Muslims against Christians and states against states. He incited gangs and disgruntled thugs to carry his message. He fired and demoted the leaders of the U.S. military, replacing them with more bobble-heads to do his bidding. He set about trying to destroy relationships with our closest allies in NATO at the behest of his mentor, Vladimir Putin. Now Trump's attention has turned to destroying, state by state, democracy at its core, the right to vote for our leaders.
You are naive to think that the DOJ is Trump's target. Pay attention to what I just said. America and all that it stands for, domestic and foreign, is his target.