What if Trolls were raptors living in a zone south-west of the Well Of Eternity (grouping Un'Goro / Tanaris) and mutated thank to the magical source?
The First Troll met the Wild Gods / Loas, and some decided to live next to their home in the Zandalar mountain. Those Trolls are the higher caste of Zandalari. Other Trolls that followed them but decided to live at the bottom of the mountain. Those are the lower caste of Zandalari.
Zandalari have a strong culture and they like to study things and history. It was forbidden to approach the C'Thraxxi's corpse at the bottom of the mountain, and to worship some Loas like Hakkar. The High Zandalari caste were not conquerors, but some of the lower caste decided that they had to grow the territory, even if they had to fight.
Then some of these lower Zandalari caste formed other Troll Tribes.
Some became Jungle / Forest / Sand / Snow Trolls, but one Tribe in particular chose to follow Zandalari philosophy and to take some distance from the other Tribes.
These became the Dark Trolls who lived in caverns, far from other Troll Tribes and leaving their caverns at night. They discovered Elune who was talking to them, and were asked to go to the Well of Eternity, where they mutated into Kaldoreis.
Kaldoreis still studied history and worship Wild Gods. They also studied the power of the Well of Eternity and worshipped Elune.
Some of the Kaldoreis studying the Arcane Magic from the WoE started to call themselves the Highbornes.
When the WoE exploded, Kaldoreis had to change their society.
Kaldoreis that lived outside Zin'Azshara and Suramar were more aligned to the Wild Gods and Nature.
These became the Night Elves and forbid the use of Arcane Magic.
Highbornes that were living in Zin'Azshara aside Azshara died or were mutated into Nagas like their Queen.
Highbornes that were living in Suramar built a new magic source, the Nightwell. They became the Nightbornes.
Highbornes that were living outside Zin'Azshara and Suramar tried to find another source of magic. Some died (in Northrend), some were corrupted (Eldre'Thalas). But some survived and had to go on the new continent (Eastern Kingdoms). These became the High Elves.
So here's the family tree:
Raptors
ZandalariZandalari high caste
Zandalari low casteJungle Trolls
Forest Trolls
Sand Trolls
Snow Trolls
Dark TrollsKaldoreisNight Elves
HighbornesNightbornes
High ElvesBlood Elves