Civil servants do not get a cut of the money from the auction; that money goes to the Treasury (or to some general fund for the public good). They are motivated by gold stars in their resumé, that eventually lead to promotions. Catching and convicting criminals yields gold stars for all involved. Carrying out a smooth auction of a weird item, with no complaints of bad press, also yields gold stars. They do not care if the auction messes the market or gets a lousy price, but they worry about doing something stupid that could stain their resumés -- such as auctioning a bunch of seized game tickets after the game, or auctioning so much stuff at one time that they cannot get enough bidders for it.
Civil servants are not immune from influence ranging from flattery to bribes. Bureaucrats act in their own perceived best interests just like everybody else does. They are not angels. They are not perfectly impartial. They are human, and when the personal benefits outweigh the personal costs for a given official action, they are likely to take it.
People with faulty ideology are capable of great evil in service to their false gods. They commit that evil with a clear conscience and that's what makes them so dangerous.