Charisma fills the room. Character keeps it full after the novelty wears off.

Charm works fast and has a short half life, because a first impression only happens once. What keeps people around afterwards is duller and more durable: being where you said you would be, telling the truth when it is awkward, remembering what matters to them. Those things are invisible at the start and decisive by the third month.

Assume the first impression is already handled and put your effort into the follow up. Answer the message, remember the detail, do the dull thing you promised. That is what turns a room full of people into people who stay.