Medical Question - Comorbidity - Ultimately who determines cause of death and how?

If someone has advanced heart disease, diabetes, cancer, respiratory disease or a combination of them and others, how would it ultimately be determined that their death was from Covid?

Let's be honest a cold could kill a comorbid patient fast, so I am struggling with this answer.

The reason I bring it up is because they mentioned a 25 year old in SoCal died of Covid because they found him deceased in a home.

Before assuming Covid was the killer wouldn't they check everything else, i.e. aneurysm, overdose, etc.


Lot's of people just plain die every single day...