Magni kept sending troops north, wildhammer dwarfs, Gnomes kept supporting Garithos and nobles of stormwind did too and them just accepting Kael's and belfs executiton not opposing it and stopping to support garithos is same as accepting it and steping aside.
Kael blamed Jaina even in dalaran about Arthases actions when scourge marched there and Kael first and foremost priority is his people and what Jaina did in dalaran to innocent blood elves during mop would cause Kael to see similarities in Jaina and Garithos.
Kael seems to be pretty okay with orcs as he was allied with them in outland for the good of his people.