(In)Security vs. (Un)Caring?

There are so many different facets to your question. If he drives a crappy worthless car, he is saying that he doesn't deserve better. If he dresses casually at elegant parties, he may be saying " I don't care about you or what you expect" or "I don't feel comfortable in elegant clothes so I dress comfortably in spite of social expectations." If his room is messy and smelly, he could just be focused on something else or he could feel he doesn't deserve a pleasant environment. You didn't say he lost his money before changing his behavior, so financial security obviously doesn't have anything to do with it. Washing a crappy car won't help if it doesn't work, so he still has a problem. If he is comfortable dressing conservatively, he may now value himself enough to care what other people think or he may have knuckled under to social expectations due to insecurity. If his room is clean, he may now care enough about himself to live in a pleasant environment rather than worrying about what other people will think about it being messy and smelly. Your choices are not mutually exclusive. You can be secure and care just as easily.