WASHINGTON — President Donald Trump suggested Thursday night that Homeland Security Secretary Kristi Noem’s ouster was less about her job performance and more about elevating Sen. Markwayne Mullin to the Cabinet post.

In his first public comments since he fired Noem, Trump was complimentary of her year-plus tenure, while he also praised Mullin, R-Okla.

“She’s a fine person. She did a good job. I’m a big fan of the senator from Oklahoma. It wasn’t a hard choice,” Trump said in a phone call with NBC News.

He also dismissed the idea that there was a “last straw” regarding Noem’s performance and instead praised her handling of the border.

Trump, however, was critical of Noem when it came to her exchange with a Republican senator this week, when she was asked during congressional testimony about her role in approving contracts, particularly a $220 million ad campaign encouraging immigrants to self-deport.

“I wasn’t thrilled with it. I spent less money than that to become president. I didn’t know about it,” Trump said.

Noem, who was facing scrutiny after federal officers shot and killed two U.S. citizens during an immigration enforcement operation in Minneapolis, was grilled by Sen. John Kennedy, R-La., about the campaign at a Senate hearing.

She told Kennedy that Trump knew about her decision to approve the pricey ad campaign, contracts for which went out through a process that limited competitive bidding.

NBC News previously reported that Noem’s remarks about the ad campaign on Capitol Hill played a role in Trump’s decision to replace her.

She faced a slew of other questions from lawmakers, including questions about whether she would retract calling slain U.S. citizens Alex Pretti and Renee Good “domestic terrorists” (she refused) and erroneous detentions by Immigration and Customs Enforcement, which is part of DHS.

Noem is staying in the Trump administration in a new role called “Envoy for The Shield of the Americas.” Trump described it on social media as a position that will lead “our new Security Initiative in the Western Hemisphere.”