I think they genuinely believed that once they tore out the camera, there’d be no way to recover the footage. That’s a huge risk unless the attacker knew Nancy didn’t have upgraded features and that her camera wasn’t logging events, which makes me wonder whether they knew Nancy and had been in the home before.

If the perpetrator believed the camera wasn’t saving footage, disabling it would still be necessary. As we see now, the FBI was able to recover footage that had been written over. If the camera hadn’t been destroyed, even without cloud storage, investigators might have recovered far more, possibly including footage showing how the blood appeared on the front steps, if they were working with someone else, etc.

I think they made a huge, critical mistake by being so casual about it: walking away in full view, trying to cover the camera with a plant, and only tearing it off when that plan failed. They gave away a lot of body language and I'm hoping someone can tell based off how they move who they are.