Nobody forced them to offer a plea deal that would keep him out of prison.
Let's be real, in the unlikely event something that crazy happened, they'd deserve the bad press for not throwing him in the clink for 5 years and giving his family time to relocate with the child support garnished from his trust fund.
The dumber option would be to let him stay at large and hope that it'll be easier to get into a constitutional case with the most stubborn webmaster alive and an experienced attorney with a specific fixation on making sure public records (which everyone already knew the bodycam footage everyone already knew would be) remain public as is legally required.
So I'm doubtful they think he'd do something that crazy. Which I guess I should reiterate extra hard because I already got a mod action despite plainly stating I wasn't accusing Nick of something else: I do not think Nick would ever Benoit his family, and I don't think the Sheriff does either because they'd have either sent him to prison or been more insistent on figuring out how his child ingested cocaine than hiding the bodycam footage.