I think Klaus wants to make a good impression on the towns people. He needs them to think that he is reasonable and Stefan is the dangerous one. He played them perfectly. Carol feels indebted to him because he spared her son the pain of turning into a werewolf for the rest of his life. Now that he is a hybrid Tyler controls when he turns. I can't imagine Carol thinking being a hybrid is worse because she received a first hand seat to Tyler's turning, and the pain it causes him. Carol, the mayor, already feels like she owes Klaus for saving her son from that painful fate. Now that Tyler is sired to Klaus, Klaus got him to bite Caroline, the sheriffs daughter. He gets to come in and look like a reasonable fellow by saving her daughter. Now Liz will feel like she owes him for saving her daughters life. I think Caroline saw the boy/early vampire that Klaus was before he turned into a monster trying to break his curse. I could see that part of Klaus slipping through occasionally, and Caroline just got to see it. It wasn't planned. Or he did plan to act like that so he could turn Caroline against her friends.