In one of many amusing anecdotes, Ostrovsky recounts how in 1989 a quintessential apparatchik, Viktor Chernomyrdin, quit his ministerial post to become chairman of a new state corporation, Gazprom. The prime minister at the time, Nikolai Ryzhkov, couldn’t comprehend why he’d do this: “You understand that you will lose everything – the dacha and the privileges?” The wily Chernomyrdin suspected that the new prizes would be denominated in dollars, billions of them.
Does "he'd do" here mean "he would do"? Why the rule of backshift of tense in reported speech is not used here, i.e. why the part of sentence is not: "couldn’t comprehend why he had done this".