Christie says not only did Steve Bannon, at Kushner's urging, fire him, they trashed the transition team's recommendations for Trump's cabinet and senior staff.
"The truly stupid thing they did was get rid of the work, too. That ill-served the president right 'til today. Because they still don't have people in key positions two years into the administration. They picked a number of people for key positions that were completely ill-suited for the job," Christie said.
Former National Security Adviser Michael Flynn, for one, Christie told KYW Newsradio.
Christie said he didn't think Flynn was a truth-teller, and that he sucked up to candidate Trump to get an administration job. Christie writes that Trump thought firing Flynn would end the investigation into whether Russia tried to influence the election.
Christie says he told Trump there was no way to make the Russia investigation shorter, but he told the president a sure way to make it longer is to keep tweeting and talking about it.
He also wrote in his new book that he regrets going to Island Beach State Park during a state government shutdown two summers ago, in which the photo of him in a beach chair spawned countless memes.
"I'll tell you, I wish I had not got on the beach that day. I write the story in the book about why I did go on the beach for an hour that day and just had the bad luck of having my one hour on the beach during the government shutdown be the time that the Star-Ledger decided to fly a plane over the beach," Christie said.
Christie says in his last summer as governor, he promised his children they could invite friends to the beach house.
He says he was heading to Trenton trying to settle the shutdown when "my wife asked me to come and spend an hour on the beach and I did. Do I regret going on the beach? Of course I do. Because I would have preferred not to have all of that attention to it. But on the other hand, I don't regret for a minute allowing my children and my wife to have that weekend in the only place they're allowed to go on the beach in New Jersey."
Christie adds Beachgate was overblown because it happened over a fourth of July weekend when there was little other news. He is currently a commentator for ABC.
When asked if he would work for his longtime friend Donald Trump now, Christie says it depends on the job, and he'll never say never.