Reasons: for blood trolls and Eredar to join the good guys for their masters are dead and gone for good.
The mighty nipple lord Zovaal, is dead!!!
The one that pulled others to his will by his Master plan!!!
The one who schemes from the shadow!!
Is now, Dead under the water,
and forgotten!
like the rest of the trash world quest bosses that we have fought in BFA!!!
Blood-trolls reason to join the alliance:
The Zandalari Trolls, hate to work with blood trolls. Hence, they joined the alliance and have a new master to look upto!
The one that recruits them to join the alliance is Sallywhite mane! The blood-trolls see her as a God amongst men!
Man’ari reason to join the horde:
The Light forge Draenei and the Draenei, hates to work with the man’ari.
Hence, they joined the horde and they are recruited by the horde council, for they are given a chance to correct their evil ways, just like the horde was given plenty of chances by the alliance to mend their ways!
So how does this work. Even if Turalyon decided to work with the Crusade because LUX VULT, Sally died in MoP and was raised as a DK in Legion, and she’s totally sowwy for all those mean and wacist things she said about the Forsaken (even though she was totally right) while she was second-in-command of the Scarlets.
The Eredar are demons now. Thousands upon thousands of years of being infused with Fel have literally turned them into demons. That’s why we had to kill them in the Twisting Neither to keep them from coming back. Why would demons join any faction?
If that’s your reasoning then, why did the blood elf join the horde?!
They hate the orcs, trolls and Undead more than the civilized races from the alliance.
The one that assisted them during the Warcraft 3 era was the Nightelfs!
So, why did they joined the faction that destroyed their homeland?!!! Or made multiple attempts to destroy their kingdom??!
Because if they didn’t they were going to be wiped out and the Horde were the only ones who offered honest help where the Alliance offered only suspicion.
The Eredar don’t have that problem, they still have the entirety of the Celestial realm of Fel to call home.
Since the Draenei took a new name and don’t refer to themselves as Eredar anymore, I think it is pretty safe to assume that when people say Eredar they are referring to the corrupted Man’ari.