I'd imagine it's quite hard to make running someone over look like an accident though. You'd have to get someone willing to do it, first of all, and then also willing to go through the inevitable police investigation, because at the very least, you're probably getting charged for death by dangerous driving. And then when his well connected business partner dies in mysterious circumstances a week later, that's getting upgraded to a murder investigation.
Yes it's not a preferred method unless it's a hit and run. Death by dangerous driving would still be classed as a tragic accident of sorts. No, him dying in a boating tragedy miles away wouldn't implicate the person hitting his partner in a road accident. Given the very wealthy people possibly involved it's unlikely to lead back to whoever wanted them gone.