I agree, people on here are obsessed with crime and these particular circumstances, but for 99.9% of the population of the US, when you have a middle-aged, middle-income corpse, tucked neatly in bed with no signs of trauma or overdose, and a respectable, apparently loving spouse living in the same home who reports it, murder is not what leaps to mind. 'Suspicious circumstances' means signs of violence, strange behaviour from the spouse, known conflict between them, and, especially, reports from family and friends that something is suspicious.
And if the millions of law-abiding, grieving people, whose spouses happen to die of natural causes, are to be put under investigation as murderers, that will not be tolerated, nor will police be able to afford it. Imagine the protests about police brutality if apparently well-behaved white people were all to be viewed as murderers anytime there is a death in the family.