It had nothing and everything to do with Rose. It had nothing and everything to do with Reinette. He was wandering through this woman's life. She didn't need him. Jeanne-Antoinette Poisson had a full and busy life. She was an educated, sophisticated woman, a wife and mother, a figure of political and cultural influence. She was involved in one of history's most famous love affairs. He couldn't touch her without making history tremble.
He wouldn't have kissed her. He didn't even know she was going to become Madame de Pompadour when she kissed him. He kissed her back and all he had to know for it to happen was how she made him feel. And when he found out her name, he didn't have to wonder why he fell in love with this woman when so many others had. He didn't realize it until Rose did. Rose took one look at him and knew, and he knew it himself and knew that she knew and knew that she was a little jealous and a lot more afraid for him.
He was a tiny part of her life and she was an even tinier part of his. He couldn't take her out of history, but he could take her to the stars and have her back five minutes later. Something like that. The TARDIS could do it, that's what it did . It made one time relate to another. He could show her any star in the sky and when he brought her back, as he must for history's sake, she would go back and finish living that magnificent, fantastic life of hers.
It wouldn't be like it was with Sarah Jane.
He went back for Reinette five minutes later and she was dead. It hadn't even been an hour for him and he'd known her almost her whole life. One hour and one life and they'd changed each other forever. How many hours were there in a millennia? How many brief candles would light his passage and be one by one snuffed out? There was no fire that did not burn.
It had a lot to do with Sarah Jane. It had everything to do with him.