So let’s be clear about this because I think you have a slight misunderstanding of the US.
The attorney general is the top prosecutor and ENFORCES federal law. The US Attorney General is appointed by the President is under the President’s purview. They are not judges who interpret the law in the judiciatu, but they enforce the law. The US Attorney General is a political appointment. The US Attorney General is not under the judiaicary branch.
Merrick Garland, with Biden's tacit approval, did not seek to prosecute Trump until congress had the made for TV hearings in 2022 because Garland made no movement on pursuing Trump.
Biden telling Garland to make the case against Trump as soon as he was in the job isn't subverting democracy, as much as Biden telling Buttigieg to figure out the airline computer problem isn't. It was Garland's job to enforce the law and he didn't.
What about the nation's tradition of the President not telling the Justice Department what cases they should or should not be prosecuting? What about prosecutorial discretion?
Anyone who was trained as an attorney in the US and has knowledge of the history of the President's relationship with the Justice Department (especially post Watergate) will tell you that that 'Buttegieg/computer problem' analogy does not work at all.