Gurubashi Empire

[Rukopashka]

What was the reason behind the sudden disappearance of the Gurubashi Empire, the powerful troll civilization that once thrived in the lush jungles of Stranglethorn Vale in the classic world of warcraft?

[Geojak]

The shattering mostly

[Galendor]

Yeah, and then civil war among tribes. And then - foundation of Stormwind.

[Shatterfury]

What was the reason behind the sudden disappearance of the Gurubashi Empire, the powerful troll civilization that once thrived in the lush jungles of Stranglethorn Vale in the classic world of warcraft?

I can`t remember too well, but there is quest chain in Stranglethorn Vale that hints about Neptulon getting pissed on the Jungle Trolls and attacking them.

[Qualopec]

What was the reason behind the sudden disappearance of the Gurubashi Empire, the powerful troll civilization that once thrived in the lush jungles of Stranglethorn Vale in the classic world of warcraft?

I can`t remember too well, but there is quest chain in Stranglethorn Vale that hints about Neptulon getting pissed on the Jungle Trolls and attacking them.

It was not Neptulon but Kraken. one Gurubashi sorcerer harmed the kraken and the Kraken sent powerful wave. But what really Harmed Gurubashi was what happened after the Saundering as trolls were suffering famine, in desperation they reached out to Hakkar and while he did initially helped them the cost for power boost was too high. This is when the Zandalari were involved the first time to get rid of Hakkar, and they were successful, but then Atal'ai sect split off to Swamp of Sorrows.
After Hakkar was defeated the Gurubashi empire splintered to smaller tribes and this is where the fights between tibes started.
Stormwind wasn't that big of a deal sure it spread it's influence, but in the end All trolls rallied and successfully raided Stormwind, there wouldn't be much left to pick if there wasn't literally Deus-Ex Machine in Medivh that intervened.

(oh so he has god-like powers to stop trolls, but he couldn't do anything to stop Scourge. And funny how he prevented trolls at first only to allow orcs doing essentially the same thing. But Trolls were actually justified in their raid- Storm was too greedy was pressing into their territories).

So Yeah, famine and Hakkar is what imo was their biggest problem.