What's going on here?

A and B have known each other for a long time (5-10 years). Person A has never really changed…always had the same personality, etc. A’s always seemed to view Person B as the same person too. Person A is a free thinker who hasn’t cared what others have thought about them and hasn’t conformed. A & B became involved a few years and still have been off and one since then. A has been hurt in the past. A & B would get close and then A would either just run or do something to ruin it…usually the run or cause a fight between them. Suddenly, out of the blue, A starts dating C, who is not A’s usual type and quite the opposite of any serious relationship A has had in the past. They fight a lot too. A has conformed to interesting and things of others when he’s dated others in the past but has dropped them when they’ve broken up. This time though, A’s not only conforming to interests of C, A is also believing things that C says (C thinks they know everything about everything) even when C is completely wrong. A doesn’t question it, won’t look it up either, but when it comes to B (whom A used to see has smart), A called B out on things a lot, even things that B is right about. A doesn’t believe B even when B shows evidence and proof of things, but if someone else says it’s true, then A believes them. A has called things out that B was right about just because C has said it was wrong. Oh, and C doesn’t B.

Is A trying to push B away….see B as something that they’re not? Is he doing this just to keep to having feelings for B…or trying not to? Is A possibly forcing themself to like C in order to not fall for B? Why? Why any of this? Why the sudden change? Sidenote too: A has cheated multiple times on C, and many of A’s friends keep forgetting that A & C are still dating and most are shocked that they still are. C is a total poser and does basically everything A likes, is interested in, etc. C has gotten food they don’t like at restaurants just because A ordered it…and rolled eyes when A ordered it before them…because they were ordering it too. A has even said that they like things about B that are the opposite of C. A is acting all smart….probably because they C as smart but yet spells words wrong and says the same stupid, made up words that C does.