The last one is more likely.
The police have approached this case with a basic assumption about the river. They haven’t taken the necessary or correct steps to cordon off the area, gather evidence and treat it as a crime scene because all along they have been treating the case like an accident.
And it might still be an accident. But what if isn’t.
Only now are the police are enquiring about enemies and stalkers. Only now are they finally considering another angle - 12 days later. This should have been done from the very first moment the emergency services arrived.
They are sticking with it now because heads will roll if god forbid their incompetence becomes public knowledge. It’s the same reason they are telling us all to shut up, because it’s hurtful to the family, and coming out publicly to say she is in the river, despite Nicolas family saying otherwise. They want this case to fade away quickly.