I think you have to understand that they care more about whether or not they can get a conviction than whatever actually happened. Then the rest of it makes perfect sense.
Arkansas is one of the least educated states in the US and one of the poorest. So, yea, there are a lot of systemic issues there.
We don't have juries because they are smarter or more fair or more just on average than a judge. We have juries entirely due to the concept of jury nullification. It's a formalization of the concept the founders sometimes expressed where "Yes I did it, but that doesn't mean I should go to jail" is an intended outcome. It's explicitly that Justice isn't the same as "follow the letter of the law".
Who says that's the case? US courts are overloaded and public defenders are massively overloaded.
Most people can't afford to hire a good lawyer, and a (let's say) 10% chance of years in prison isn't worth gambling versus a plea deal to them. Prosecutors know this, file massive scary charges, and motivate people to settle regardless of innocence or guilt.
The plea deal offer kind of says it all, if this reaches the court it will either very quickly be thrown out or they may drop it because it's not worth the time.
The detectives screwed up by doing a piss poor investigation and identifying the wrong suspect (who is a victim herself in this crime).
The prosecutor cares more about whether they can sell the flawed case to an Arkansas jury or use the low plea bargain cost against the high legal defense cost.