Who made rasta popular among metal fans? When did it all start? Is it sub-genre specific?

i think its mostly a nu metal thing.

I think it all started with jeff walker

This dude with short black dreds got his ass kicked at this local black metal show because he looked like a Cradle Of Filth fan, lol.

The origins of them though...I don't know but some people need to learn that they don't suit everyone.

Crust. Punk.

I know Rob Zombie had them back when he was still in White Zombie, and used didn't go by "Rob Zombie". And White Zombie started in the Mid-Late 80's, so he's one of the first really popular ones I can think of.

he's gone by the name Rob Zombie even since the days of White Zombie.

I'd say it has more punk/crust origins given that there seems to be an ecofriendly/activist connotation with both punk/crust and dreadlocks. Just an assumption, of course.

If you read the linear notes of the earlier EPs and the first album by White Zombie, he isn't listed as Rob Zombie. I think he chose that moniker during the "La Sexorcisto" era White Zombie.

But that's getting off topic.

I reckon it happened this way...

It started in the 70's when Reggae and Punk were influencing each other.
The punks had dreads first.
Punk grew more extreme and evolved into Hardcore, and that evolved into Grindcore.
and of course Carcass were Grindcore.
Dreads were adopted from Grindcore into the Death Metal scene in the early 90's.

When Korn emerged in the mid-nineties, dreads were a wigger mallcore thing all of a sudden? I don't understand how that happened.