This is looking at two effects and deciding one of them is the cause.
Saudi Arabia is a close ally of the US. That's the really horrific truth, and that's why Trump has business there and not in countries which the US is less friendly with.
We can't really know whether it's because of his biz interests or because America is friendly with the Saudi regime.
This is why Trump's refusal to divest himself from his businesses is an unacceptable conflict of interest even if he insists it is fine and there are no grounds to question it.
Saudi Arabia is a close ally of the US. That's the really horrific truth, and that's why Trump has business there and not in countries which the US is less friendly with.