6.5CM is not alone also way over hyped:
350unlegendary
6arc(not a 308)
300prc(actually the same as a 300wm)
6.8western(don't even me started)
All 5 of these calibers are very useful and fit in very necessary places on the spectrum. All 5 were marketed way over their potential. However, can we really blame Hornady/Winchester/Browning for this? Look at what happened to Federal's 224valkirie. If your a manufacturer and you want to innovate you have to sell it in a way that enough people will buy it to cover the cost of something new. The real problem isnt with Hornady/Winchester/Browning/Federal/Remington. The problem is with our generation of IPhone, ticktock, YouTube, Twitter users. Everything is instant gratification and people buy the thing that looks the flashiest on the surface.
Experiment:
find someone you know who owns no guns and has never been hunting. Talk to them about guns and hunting. I'll bet that if they can be interested in in it at all the first thing they want to buy for hunting is an AR15 in 556! Nothing wrong with that for Hogs and southern deer!
Funny story:
I had a hipster friend of mine ask me to help him build a rifle because we already built an AR pistol. He tells me that he wants it to be in 7.62-556 and be as powerful as a 30-06 but as light and short as an M4! This man is an NCO in the US Army! He got discouraged about it and never built it after I tried to explain to him that you couldn't fit a 30-06 in a stanag magazine. Lol