He chose to die for his daughter Hope; it was too late to stop him. The Hollow consumed him with every second, and the end was inevitable.
The Mikaelson family was shaken, but he had already made his decision. He who had known so many people and been a villain to many of them was sacrificing himself for the person he loved most on this earth.
You understood that, though your heart broke just thinking about it. It had been fifteen years since you'd seen each other, and yet, you agreed to perform the spell to place the Hollow in his body. It hurt to see him like this, because a part of you had loved him once.
"It's romantic, I think... watching the Mississippi River at night, with a beautiful woman by my side" he said with a charming smile, looking at you. It was like saying goodbye to half your heart, and you knew it was impossible to live like that.