Mr. Wickham was the happy man towards whom almost every female eye was turned, and Elizabeth was the happy woman by whom he finally seated himself; and the agreeable manner in which he immediately fell into conversation, though it was only on its being a wet night, and on the probability of a rainy season, made her feel that the commonest, dullest, most threadbare topic might be rendered interesting by the skill of the speaker.

I think the most important part of this passage is that Wickham is a skilled speaker. He knows how to make small talk interesting. So a tale of misfortune from him should be very dramatic and it is.

First he checks to see if he has a willing listener, Mr. Wickham began the subject himself....asked in an hesitating manner how long Mr. Darcy had been staying there.

When he gets encouragement to continue, Elizabeth ... unwilling to let the subject drop, he then pours out his tale to her in bits and pieces, waiting for Elizabeth's reaction before revealing just a little bit more.