Looks like betrayal is in their blood.
Azshara and her acolytes betrayed their own people to the Burning Legion.
High elves betrayed the Alliance over the actions of one man, and joined in the Horde. Of course it only took one man, betrayal is in their blood.
Kael'Thas betrayed his own people to the Burning Legion, same as Azshara.
Elisande betrayed her own people to the Burning Legion. Yes, it's a very recurring theme when it comes to elves.
Thalyssra betrayed not only her Alliance helper but also the Alliance who came to liberate Suramar, only over the words of Tyrande. Once again, it was easy since they're so quick to turn on their allies.
Void elves betrayed their own once again and joined back with the Alliance.
Why are we even trusting an elf?!