Here, we have to posit a conspiracy powerful and cold-blooded enough to commit and cover up murder, but which is too inept to to put any significant distance between (presumed) co-conspirator and victim. I think we need to give equal consideration to the possibility of it being a 'doorstep suicide,' where a troubled person ends their life in proximity and as a reproach to a perceived antagonist, if only because of Occam's Razor.
Occam's Razor cuts both ways when dealing with neurotic geeks or with megalomaniac billionaires.
I mean, if you're going to go down that route why not stage the suicide in the lobby or even the inner sanctum of the putative megalomaniac's office, which would be even more dramatic and damning? The obvious answer is 'because that would be suspicious,' which invites the rejoinder 'and doing it 25 feet down the corridor isn't?' If you have a wicked plan to destroy someone's reputation, you might as well pick the least ambiguous way of doing it.