I think you're underselling the challenge in the parts of the business that aren't coding. Which is exactly why this guy's decision is such a bad one.
He's basically said "I have skill set X, which I'm trained in and have been honing for years. For my company, I need skill sets X and Y. So I'll do Y and find someone else to do X."
No matter what X and Y are, that's just the wrong way to solve that problem. The key issue in this case being that he is assuming the marketing/user acquisition stuff is so easy that he can just pick it up on the fly with no prior experience.
OK, but here are your outcomes if you are good at X and need X and Y:
You do X, hire Y - You have one skilled person, one question mark.
You do Y, hire X - You have one unskilled person, one question mark.
Seems pretty simple to me that the first is better. I suppose that you could make the argument that Y may be easy to pick up, but if that's the case it should be all the easier to just hire someone else with a proven track record.
My thought exactly, those two question marks aren't equal. One I am capable of evaluating, both before and after I hire for the position. The other I am incapable of evaluating both before and after I hire for the position.