MTV CEO's Who Destroyed Metal.
 

So, was watching some recent interviews from some old metal band members, and I guess the news is trying to blame Grunge for being the reason why Metal music pretty much died off, but the band members are saying it was a new CEO of MTV that came on at the time and he hated Metal and just refused to play it. Eventually would do the same with Grunge. So, does anyone have any idea who this CEO would have been?

Maybe David Geffen.

In an alternate reality, he doesn't sign Nirvana and the Grunge explosion peters out? Does Nevermind become a Suppop release?

He seems pretty instrumental (pun intended) in the rise of grunge.

I'm not sure. I'm going to assume this started happening around the mid 90's but some say it was around 1992 to be exact.

It seems a Doug Herzog is the one that started the reality craze on MTV, but I seen people blame Brian Graden as the one who pretty much destroyed MTV.

Sorry I completely misread your OP. MTV CEO, not music CEO.