It's the prosecutors job to look at the case to determine if there is enough evidence there to file charges and secure a conviction. If not there would be so many cases going to court it would be insane and also a waste of tax payers money. Sure, they could've worded it differently, but regardless, there wasn't enough evidence to proceed with charges apparently.
But the prosecutor did not say there was not enough evidence. He used the term "beyond a reasonable doubt" which would imply that in fact there was evidence but that he made an assumption on how a jury would decide, even though that's not his job... that's a jurys job. That type of action by a prosecutor should be troubling in any case... this one or any other case.
I'm sorry but that's not how it works. Maybe ideally that's how it should work but it's not. Most cases don't actually go to a trial before a jury, regardless of whether they involve high profile defendants or not.
A prosecutor ethically should not bring a case which s/he does not believe he can be proved beyond a reasonable doubt. S/he might believe the accused has committed a crime, but not beyond a reasonable doubt based on the evidence. If s/he brings a case for which s/he does not have that level of evidence, that would be unjust and a waste of the public money. The standard of evidence for the title IX investigation is much lower -- based on weight of the evidence and preponderance of evidence. If a title IX investigator believes that all of the evidence (including hearsay evidence) supports a complaint, then the accused can (must?) be held responsible, according to the Office of Civil Rights of the Department of Education. Like it or not. However, the title IX person quoted in the JS article says that investigation will completed within 60 days, so that covers the rest of the season, easily. findings could affect player eligibility next year, though, as title ix sanctions include expulsion. If the reporting party is not satisfied with sanctions, then s/he can appeal or complain to the OCR.