Yours is an appropriate question. The answer seems to be that attorneys for Cochran were investigating themselves and then turned over what they found to the police. I don't know if that is a good enough answer.
It should also be noted that the McDaniel campaign never contacted Cochran to say "Hey, this crazy supporter of ours took and posted video of your wife in her nursing home room and we told him to take it down. We had nothing to do with it but we're sorry this happened." Nor did the McDaniel campaign itself notify the police that they were aware of this illegal activity conducted by a supporter. That would have been a very smart thing to have done, inoculating themselves against any claims that they were behind it.
Given it was a crazy the mcdaniel campaign had had issues with in the past I’m not sure there were any good avenues for them to take. Any indication of knowledge of the video would be taken as an indication of guilt.
Given that the facility in question is obviously not a safe place for little old ladies, I wonder if the cochran group has even moved her somewhere presumably safer?
Or maybe, like his DC ‘lifestyle’, his campaign has taken precedence over her wellbeing.