Why did mr darcys demeanor toward other people change from one of indifference to one of courtesy and hospitality?

Answer 1

Darcy was clearly shocked by Elizabeth's rejection of his proposal of marriage. He clearly was deeply in love, but he fully expected her to accept. In rejecting him, she was rejecting a man other women thought was desirable. He had commented on the fact that her chance of being married well was greatly reduced by her lack of wealth and connections, and she was refusing wealth in favor of taking her chances with marring someone unknown or being poor. Her rejection made him think about what was wrong with him that she would not want him.

We do not see Darcy's self examination. She had complained about various things in rejecting him, some arguably true, and at least one thing clearly wrong. He had to think about the things she said. In truth, he had complained, for example, about her mother; but Elizabeth's mother was no worse in any respect than his aunt, except for a difference of wealth. He had complained about her family in general, but was surprised to realize his complaint had not been correct when he met Mr. and Mrs. Gardiner, took them for people of fashion, and learned they were her mothers brother and sister in law. Later, when he heard of Lydia's elopement, he clearly knew the same scandal had very nearly been visited on his own family by the same man, and would have been except for chance intervening. In the end, he had to realize the two families were very much alike in many ways.

Elizabeth had talked about his faults on a number of occasions. He had said he was resentful and unforgiving. And yet, Elizabeth clearly blamed him for things he had done that hurt her sister, Jane. He could not deny he had tried to separate Bingley and Jane. In order to deal with Bingley honestly, he had to confess this to him. And in doing so, perhaps even contemplating doing so, he had to admit he had done something that had all the potential of being as bad as what Wickham had nearly done to him.

He was left with only a single reasonable option, which was to respect other people, even if they had their faults.

However it happened, it is an interesting story, and made all the more interesting, perhaps, because the author chose not to tell it. Instead, she left it to our imaginations.

Answer 2

Darcy wanted to win Elizabeth's favor.