I agree on many points you make.
I am not so sure on the investigation being terrible.
If that tip wasn't misfiled sure this would have been over quickly and all the other stuff never would have happened. BUT who is at fault for that tip being misfiled? I think DD writing "who are the 3 girls" on there likely was the focus of whoever labeled it as cleared. So if they knew who the 3 girls were and didn't read the rest of that tip narrative, then i doubt they had any idea this was a man there during the time of the killing.
We have a killer that didn't leave DNA or fingerprints. He also was not recognized by anyone that saw him so the girls didn't recognize him to say hey that is RA.. and same with BB and SC. So what was LE left with other than RA calling in? If he didn't do that, he wouldn't be on trial right now and that isn't any fault of LE because how can they find someone that left zero clues.. well that bullet and his car on video, but they can't check every house in Delphi for a gun that left the bullet.
I've just seen some suggesting that if RA didn't call in he wouldn't be caught and that is likely true, but that doesn't mean LE didn't do their job. It means he would have gotten away with it.
I think they worked their butts off trying to find this killer and not knowing that tip was there all along doesn't mean that they did a terrible job. I think they ran down every lead they could and ruled out so many people.. 10,000s of tips.. And interviews being erased doesn't mean they did a terrible job, they did their job interviewing these people AND ruling them out. The D only wants to say that was bad because they want to blame those people, but LE did their due diligence trying to find this guy.
Two things can be true, the investigation was lacking and they are still able to prove their case.
One man says he was there that day during the specific time in question.
One man other people saw that day.
One man who admitted to (almost certainly) seeing the people who saw him.
One man who was admittedly dressed as BG.
One man whose car was caught on camera.
One man whose phone was suspiciously not caught up in the geofence despite his claims that he was using it.
One man admitted to drinking alcohol, going to the bridge, spotting the girls, following them, planning on raping them, getting disrupted,"cutting their necks," making sure they were dead, and covering them with sticks.
One man owned a .40 caliber handgun that matched the unspent cartridge found between the bodies.
One man confessed over and over.
One man said he stole a boxcutter from work, used it in the murders, and disposed of it in a CVS dumpster.
One man whose mental health declined after the murders.
One man who conveniently changed his timeline after he knew he was a suspect.
One man who ticks practically every box in regards to someone who has historically committed this type of crime (suicidal, substance abuse, depression, admittedly under the influence at the time of the crime).
They’ll never find a better suspect than that.