I agree it’s a travesty, but how would a prosecutor make that case? The evidence doesn’t exist.
I admit I haven’t been following this much. It doesn’t matter what people claim, nor whether you believe them or not. What matters to the DA is what he/she can prove. So in that light it comes down to a discussion/argument on perspective and judgement. Is there enough physical evidence and credible testimony to counter whatever defense he could put up? Is a “beyond reasonable doubt” outcome likely? DA may have looked at what he/she had in-hand and said it’s just not close enough to a yes to make it worth pursuing - yet.