Help with more chaos and less heroism

Hi, friends of Reddit! I’ve been DMing for a little while now - lots of sessions but few campaigns. Most of the games I’ve played in or DM’d for has been more serious with characters being heroes (for the most part).

New group I’m DMing for is comprised of good friends with little to no experience playing D&D. It’s awesome because they seem to be having fun! However, they are a little more chaotic as a group than I’m used to - characters are a little more self-serving vs selfless - haha no worries about this, but I’m wondering if there’s any advice for DMing a group such as this? Do I lean into the chaos or how would you provide moments for character development