It is a little confusing, they ruled that the search was not legitimate, but this didn’t end up helping the defendant? I’m definitely missing an important nuance here but I’m not sure what it is…
(mostly true -- for instance an officer can generally commit innumerable felonies as long as nothing they do violates your personal constitutional rights -- rarely is evidence thrown out because it was obtained in violation of a statute unless that statute includes a provision for exclusion, e.g. wiretapping laws)
Parallel construction means they have an illegal bugging device in the courthouse bathroom, and use a conversation that you have with your attorney to identify a witness. Then they independently arrest the witness for something and pressure them to testify.
It's using illegally obtained evidence (like an NSA wiretap) to point the detectives in the right direction they would have otherwise never probabilistic-ly searched.