Her experience as a marketer makes her good at finding the right talking points. There's no depth to her and, while she tries to claim she's not another politician, her laughable defense of her HP tenure makes her just as much a liar as the worst of them.
Basically - I can't think of better training for being a political candidate than working in marketing for several years and then serving as CEO of multiple public companies. You have to look and sound convincing and competent without necessarily being so, and you have to be able to condense big, complex ideas into short, simple sound bytes.
She's an expert at selling things. There is a reason Oliver Stone opened the movie
Nixon with that old-timey corporate training video where the guy says, "And remember - what you're really selling is yourself!"