That was the reason Matt left.
Because he couldn't bear being on set with her, travelling around the world with her, just looking at her knowing there was another person in her life who loved her, took care of her, kissed her and slept in the same bed as her at night.
And that person wasn't him. No matter how much he wanted it to be him, it just wasn't him. It was Richard.
And god Matt loved her. Jenna. He could get lost in her eyes, stay in her arms and cling to her hand for the rest of his days. But love is a complicated entity – he knew that much. And his dreams were just dreams, and staying and having his heart broken wouldn't make them a reality.