I’m always a fan of transparency content; thanks for being open and sharing your results. I would say one of the key things about your HARO experience may have been that you admit you went after anything, and not things specifically relevant to your target audience.
I’ve used HARO for years, and have ended up getting some big mentions (including a Forbes article!). But, I focus the queries I’m responding to on things that are relevant to the company I’m working for.
P.S. A little funny that I read this after looking you up…because you sent a HARO response to a query I posted ;)