He knew. He knew it was too late for him. He loves you, but you're going to leave him. You had always been by his side, but he took you for granted.

He ended up loving someone else who ruined his life. But you were still with him. That made him realized how much you have sacrificed for him and he loves you.

But you wish to leave. But you can't leave him like this, he needs you. He's attached to you

He'll make sure to make you stay, even if he have to beg on his knees.