Yes, he's fun. Yes, he's marketable. Yes, he produces fun fights, exciting finishes and is a knockout holder, and all that.
The reason the UFC signed him to that big of a deal is simple. Keep him away from Ngannou.
Their first fight was a snoozer, but it's still a win Lewis holds over Ngannou and a rematch would do big business outside the UFC ( huge contract on the line, better storyline than their first fight, big, fun fight for casuals and hardcores alike).
Dana will do anything to deprive Ngannou of worthwhile opponents.