I remember the Watts murder case where Chris Watts killed his wife and kids, but he called the police to claim some murderer came to the house and did it. Anyway, they brought the dude in to interview him, and Chris has no indication he's there because they suspect he did it; in his mind he's treated like the victim. The police speak with him in a manner that suggests that they're trying to do good by finding the person who killed his family. In fact, it's quite possible that they only slightly suspected he was lying and was largely telling the truth. Anyway, there's a video of his confession where, prior to him completely giving way, they give the guy a lie detector test. The polygraph is a complete interrogation ploy by the police to pry open the guilty, it serves no other relevant purpose as the "passing" or "failure" is not admissible evidence in court; it's just a psychological tool for interrogations. They grill him about how he "failed" the test and how things aren't adding up, which prompts him to start explaining away the 'failures' because he thinks it's going to legitimately hurt his case. If you're an actual victim of a family murder, I can see how this is infuriating as a victim. But the only reason it got to that point was because the information he gave the police didn't square and they have to proceed in the investigation process like that. They have to go down these roads. The whole thing started with Chris calling the police as the victim and somewhere along the line, the info he gave didn't reconcile with the info his neighbors gave. He initially said that his house was broken into from the front, but his neighbor's security footage showed there was no intruder to the front of the house. If Chris would have given them info about a break-in from behind the house, then they wouldn't have pursued that inconsistency. Instead, why he thought they broke in from the front and how readily he was able to communicate that to the police and why became relevant to solving the crime.
TLDR: If the police didn't get as much info as possible from every source they may have found relevant, they would never have been able to use the security footage to cast doubt on Watt's claim. Their job is to get down to the bottom of the claim, even if it is an inconvenience to the alleged victim. Even if the roads they lead down may be hurtful to someone telling the truth. It's not extraordinary that the cops would want all of Smollett's info, especially of how sus his story was.
I gotta actually get back to work and shit.