[quote=thewizardguy]
I still don't get how the protoss were defeated. The reason they fight on equal grounds with the zerg is because almost all of them are dead, but how did they all die in the first place? Imagine a fight where there are just as many Zerg as there are Protoss. The Protoss would OWN the Zerg.
[/quote]

Well, a xel'naga named Amon basically buffed the zerg extremely, and used them to wipe most of the protoss out.