Nevertheless, the fact that the DM had the footage means that the householder offered it to them ahead of the police. If it had been the other way round, the police would have prevented it ending up in the MSM like that. By extension, that means that the police still hadn't, at that time, got round to approaching householders for door cam footage despite - as you say - the limited area of relevance. I do find that quite poor, although I think the progress that's been made since is impressive.
As for why it wasn't treated as a murder more promptly, I still find that odd. Suicide or natural causes both seem like a leap considering she had a head injury, and people who die of natural causes don't usually manoeuvre themselves into shrubs while doing so. I would be very interested to know the rationale for waiting until after the PM to open an investigation, but meanwhile I'd be satisfied with arrest. With that footage, you've got to hope it won't be long.
JMO