The father and mother didn’t help their case when they got rid of the rug she died on because they were renovating the house.
To me, that was very strange. If it had been my daughter, I could have waited to renovate until the police were finished collecting evidence.
In most criminal cases, for investigators, evidence builds quickly toward a conclusion as to guilt, and then a confession or CSI reports bring the case to beyond a reasonable doubt. Or, less often, cases stall for years until something breaks that shows who is guilty. That has not happened (yet) in the JonBenet Ramsey case.
Moreover, the first set of investigators believed the Ramsays were guilty (or at least complicit with the son) and got a tentative vote in the grand jury to charge them. But the head prosecutor intervened and said no because the case was too flimsy to take to court. And then evidence accumulated in support of the Ramsays.
Unfortunately, by focusing too soon on the Ramsays, investigators lost the chance to do the essential shoe leather work of tracking down and interviewing all the neighbors with a record of sex offenses. That might have found a suspect. Now it will likely come down to DNA or a jailhouse snitch.