It is very difficult to recuse a judge. The legal community is somewhat incestuous. For example, judges aren't conflicted out due to lawyers appearing before them who contributed to their election campaigns. I literally worked on a Judge's campaign responding to political, union, and business groups surveys which led to endorsements and donations and the Judge didn't recuse herself when I appeared before her.
The law firm in question, Paul, Weiss, Rifkin, Wharton & Garrison currently has over a thousand attorneys. In that Plaintiff's counsel may have worked with the Judge over 30 years ago probably isn't enough to conflict out the Judge.
Yeah, it’s probably not. Look at all the DoJ lawyers who go on to become federal judges. That doesn’t mean they can’t hear cases involving DoJ, just not cases that their former employer was working on while they were there.