Ambessa truly is both the fox and the wolf

We got to see a bit of her more brutal "wolf" side in season one and now in season two, we get to see her "foxy" self-orchestrating events in Zaun and Piltover for her own benefit.

Double-crossing Salo and naming Caitlyn the commander of Piltover was an extremely smart move. Salo is a crippled man with no fighting experience at all; I bet he would command ZERO respect from the Enforcers and the topside elite would quickly figure out how much of a puppet the guy is.

Caitlyn is from a distinguished patrician family so we see how quickly the elite accepts her

And further, she is clever and clearly has the respect of the Enforcers given how quickly they started clapping with the Noxian soldiers.

And, despite all that and how qualified she is, Caitlyn is also young and grieving which makes her vulnerable to the manipulation of an older, more experienced woman.

This echoes a bit of that scene in season 1 in which Mel also tries to set up a puppet ruler on her childhood flashback. Ambessa is doing a similar thing but in a "harsher" way fitting her more militant nature.