They aren’t married so I don’t really consider this infidelity. Sorry, no disrespect to people who think a long term boyfriend or girlfriend is the same as a spouse - but it ain’t!
Anyway, people cheat because of 1) the thrill and 2) the way the other person they are cheating with makes them feel.
They may love their spouse and have no intentions of leaving them. But the feelings they have when with their lover cannot be replicated by the spouse. If they could, they wouldn’t be cheating. Either the spouse is refusing to meet those needs, doesn’t know how to, or just doesn’t feel like it. Yes, the “victim” being cheated on has some culpability because 9/10 they know their partners needs are not being met.
People need to grow up and stop thinking that people in a marriage are invisible to everyone else and that being married means their needs are met like a check box.
And I don’t feel sorry for Nia Long she comes across as arrogant and birdish.