

So when protoss wins it will often look like a complete domination and people will tend to conclude imbalance. It’s because Protoss is a gimicky race that swings into one player’s favour very easily.

The Conclave actually sent Tassadar to burn any human worlds where the infestation popped up, which he did in the case of Chau Sara, Mar Sara, and (I believe) Antiga Prime.

Keep in mind that, as mentioned, the Protoss were no friends of the Terrans once it became clear that the Zerg were infesting Terran worlds. So with the books and extra material aside, they make it clear in game that Mengsk betrays Kerrigan because she is quickly becoming a tool he can no longer use, with her arguments and opposition to his plans.
