https://innocenceproject.org/dna-exonerations-in-the-united-...
A friend, A former police officer, said the most astonishing thing he learned as a rookie was how easily some people would confess to crimes they could not possibly have committed. Such persons were usually not very bright and, after hours of interrogation, could be convinced that they had indeed done a bad deed.
But given that you just confessed guilt, a not guilty plea is going to raise eyebrows and potentially end badly.
Defendants are constitutionally entitled to a jury trial. Even if they were caught on 4k video, with their face fully identifiable, their fingerprints all over the blood scene, and they walk straight into a police station afterwards to confess.
A defense lawyer with a client who confessed on video has an extremely difficult job; they must try to present a credible case while also not suborning perjury or violating ethical rules. Very frequently, they're not going to have a "logical" case; they're simply trying to poke whatever holes they can in the prosecution's case...because the Defense is not constitutionally required to prove anything (unless they're attempting to prove an affirmative defense, and if they were you'd know because the judge would explicitly tell you).
On the other hand, if the prosecutor and the police and the forensics guys were all as incompetent as you claim, the defense might have gone to trial despite the taped confession because there was a chance they could prevail with a jury if the prosecution messed up presenting the case. I won most of my jury trials because the prosecution messed up.
If the investigation had been just workmanlike or followed basic protocols I cant imagine any defense attorney would have wanted to take it to trial. Though perhaps they still didn’t want that but their client demanded it. I of course couldn’t know that.
It's very likely that the prosecution and defense had a plea deal that fell through at the last minute when the Defendant unilaterally decided to go to trial, necessitating a trial that neither side had prepared for. It's basically what's been happening with Twitter for the past several months, and we don't all assume that the staff at Twitter is incompetent.
Don't assume incompetence about something you know nothing about.
Are you sure they were all bad at their jobs? It's certainly possible. But it's also possible that you simply had unrealistic expectations for what the process looks like, exemplifying the "CSI Effect".
This is why I find these sort of pseudo-anonymous anecdotes very difficult to judge; I know neither the details of the case, nor you personally. It's like trying to get reviews for headphones online... suppose I read a review from somebody who says the headphones sound worse than a skinned cat. Is that review from a typical headphone user with reasonable expectations for sound quality? Or is it from an audiophile with very high, perhaps fanciful, standards? I have no point of reference for determining where that person is coming from.