Yes, people have a capacity for treason. The biggest discovery of the year right here. But them having said capacity isn't an argument against them being traitors. Trying to invoke some mysterious and utterly meaningless "Horde spirit" is even less of an argument. Especially after your glorious Saurfang himself called Sylvanas the true heiress of Horde's legacy.
Nope. They left after stopping his advantage. The Night Elves pushed the Horde back only in their Ashenvale questline, which happens way later. But thanks for making it known you don't know what you're talking about.
At this point your argument is so off the rails you're not even aware of what you're trying to argue against. Vide you constantly shifting the goalposts. Which led you to arguing in favor of my own point:
Not only are you moving the goalposts again, but the Horde being in Ashenvale doesn't mean they had any significant success there. Unless you're capable of providing evidence of such successes? Of course you're not.
Because Garrosh totally didn't seize the chaos of the Cataclysm
Ah, wait, he did. And he attacked while it was still ongoing, as opposed to Sylvanas attacking only after the Legion was gone. This tangent totally didn't backfire for you.