For Korsak, it's the way they are when they're together. He's been married four times after all, and while the first three hadn't lasted there had been love there, to begin with. When the two of them are together there's a fairly good chance that they'll forget about everyone else around them, purely concentrating on each other.
He's always been there for Jane if she ever needed him for something work-related, and he would have been more than happy to help her after the Hoyt, but she hadn't wanted it, but he knew that she had now opened up the Maura about it all. Not only was Maura professionally able to help her, but because of their personal connection, which was clear as the noses on their faces, Jane had opened up to Maura more than Korsak ever would have thought her capable of.
He knew why she was closed off, she did after all work surrounded by men, but when she was with Maura, Jane was always a lot more open. Korsak was always happy to see them together, and he hoped one day that he would see them admit their attraction to each other. With Kiki he was happy, and he really hoped the two of them would find that happiness with each other.