The lawyer, Erez Reuveni, answered most questions asked by Judge Paula Xinis with "I don't know why" or "I haven't been told why". For example, when asked on what legal basis or authority the US government had deported the man in question, Abrego Garcia, the lawyer said he didn't know.

"From the moment he was seized, it was unconstitutional," Judge Xinis said during the hearing. "If there isn't a document, a warrant, a statement of probable cause, then there is no basis to have seized him in the first place. That's how I'm looking at it," the judge said.
(Source is linked article)

The judge also questioned why the U.S. can’t get him back. Reuveni said that was the first question he asked when he was assigned to the case.
“I have not received today an answer that I find satisfactory,” he added.
Source: https://www.pbs.org/newshour/politics/judge-orders-return-of-maryland-man-wrongly-deported-to-el-salvador-mega-prison

The judge also asked for evidence that the deported man, , was a member of the gang MS-13. But Reuveni couldn't provide

Xinis noted in her opinion Sunday that the Justice Department presented “no evidence” that Abrego Garcia belongs to MS-13, effectively abandoning that position in her court.
Source: https://www.politico.com/news/2025/04/06/judge-order-return-man-el-salvador-00274526

Finally, the lawyer made one last request, to wait and let him ask his client - the US government - to try and return Abrego Garcia first. But look at how he frames his request:

“I would ask the court to give us, the defendants, one more chance to do this,” Reuveni said. “That’s my recommendation to my client, but so far that hasn’t happened.”

Basically telling the judge "I've already asked and got told no way but let me ask again" as a surefire way to make the judge ignore the request.
Source: https://www.politico.com/news/2025/04/05/doj-lawyer-leave-deportation-00274412

Admittedly, it's not entirely clear yet that this was deliberate malicious compliance - but Erez Reuveni has nearly 15 years of experience and almost certainly would have known how to make a more compelling argument before the court, had he been so inclined.
Source: https://www.politico.com/news/2025/04/05/doj-lawyer-leave-deportation-00274412

In fact, the current US attorney general said this about the matter,

“He did not argue,” the attorney general complained, although Reuveni did argue that Xinis had no jurisdiction to consider the case. “He shouldn’t have taken the case. He shouldn’t have argued it, if that’s what he was going to do,” she said. “You have to vigorously argue on behalf of your client.”
Source: https://www.politico.com/news/2025/04/05/doj-lawyer-leave-deportation-00274412

He could have not taken the case, it seems. But he would have known that if he passed on it, someone else would argue it, and that someone might do a much better job in front of the court. So it's probable that he took it upon himself to throw the case and save this man.

Alas, it seems his bosses saw through that. Even though he did argue that the court had no jurisdiction to consider the case, as he was likely ordered to do,

Deputy Attorney General Todd Blanche sent Reuveni suspending him for failing to follow “follow a directive from your superiors” and “engaging in conduct prejudicial to your client.”
Source: https://www.politico.com/news/2025/04/05/doj-lawyer-leave-deportation-00274412

To me, that reads as if Blanche had figured out that Reuveni had complied with orders, but only maliciously so, and thus treated it as a case of non-compliance. (In truth, malicious compliance here hurt the government's case worse than actual non-compliance - refusing to take the case at all - would have.)

I'm not 100% sure I'm right - after all Erez Reuveni is a professional lawyer and thus knows what to say and not say in public to protect himself - but if I am right, then I'd consider Erez Reuveni a true USian hero.