Anthony is probably on Kyle's level. Casey is on Kyle's level as well. Hopefully everyone can stop pretending Kyle brainwashed her to be this way. She's just a lame person with very little going for her. Kyle is a prize to her.
It's not necessarily "brainwashing" but it's key manipulation that narcissists do to everyone around them which creates a toxic codependency. She's just apparently foolish, naïve and low self-esteem enough to continue to fall for it when there's so much information available to her. The way she looks at him like she's so proud when he acts like an infantile loser never used to happen, but she's clearly regressed into this weird mother-child/caretaker role.
One could say that her life was so lame before Kyle too, that she also sees this as an upgrade because she gets to play house and has thousands of 'fans' who worship her.
With Anthony, he strikes me as a narcissist also, and they flock to each other because ego is pure beauty to them. He seems enamored by the more grandiose narc (KP). They don't often like each other but they can both turn on their charm while trying to use one another for their own benefit before discarding them. We we know KP can put on the façade, just look at all the people who swoon over how "nice" he is when they meet him in the parks.