I guess he wouldn't think that much in that time, he was a

lonely man, he and his wife's love had died out, so he looked for a short term partner, I should say he like Miss Wang, since she was pretty, sexy, seemed to understand him well, and more important was that he thought she was trust worthy(in his position, that was the most important factor). He enjoyed this relationship. So he gave her a big diamond ring and said some sweet words to please her. In reality, the modal of Mr. Yi had several girlfriends before, just kind of like Eileen Zhang's first boyfriend.