Because of the explosive politics involved, the FBI Director knew about this, Assistant AG Rosenstein knew about this, AG Sessions new about this (he probably alerted Trump), and many others were aware this would happen.
Trump and his alleged-attorney probably had the same kind of omertà-relationship that John Gotti had with his legal mouthpiece, Bruce Cutler. Although Cutler was never convicted of any crimes, he was removed as Gotti's lawyer because he probably knew of criminal activity by his client.
From Wikipedia:
When Gotti was indicted in 1990 for the 1985 murder of Paul Castellano and several other crimes, presiding judge I. Leo Glasser disqualified Cutler and two associates from representing Gotti. Citing evidence from wiretaps at Gotti's Ravenite club, prosecutors contended that Cutler and his colleagues may have known about criminal activity. Since the attorney-client privilege doesn't apply in these circumstances, prosecutors argued that Cutler was "part of the evidence" and thus liable to be called as a witness. They also argued that Cutler had represented other potential witnesses and thus had a conflict of interest. Glasser sided with the prosecutors, contending that Cutler was the "in-house counsel" for the Gambino family.
Sound very familiar, doesn't it?
By the way, want to know who finally convicted the Teflon-Don, as Gotti was known? Bobby 3-Sticks!