[ahahahahah]

Why does it matter? Do you think it's impossible to commit suicide in that way? Do you think that the coroner has less information than you do about whether this is suicide or not? Do you think the coroner has less training and knowledge than you do in this area?

Or is it just that conspiracy theories are fun?

For reference, it is rare but not extremely so that people commit suicide with a gunshot to the back of the head. And in fact, you can find studies like https://pubmed.ncbi.nlm.nih.gov/38471138/ that explicitly go into ways to distinguish between a suicide and a homicide in such situations.

[serf]

a conspiracy theorist wouldn't accuse the coroner of being poorly trained.

They would say that the coroner was highly pressured, in cahoots, or paid.

conspiracy theories generally don't allow naivety/neglect/negligence/error to be a reasoning for any of the steps; everything is a cog with a purpose.