User blog comment:B214/Volume 17 spoilers./@comment-24053170-20140220004506/@comment-1359322-20140220083040

Because Ddraig said that Tiamat hates him, which sounds like something Issei in the past would do, misunderstood Tiamat's intention. Ddraig and Albion were constantly fighting, Tiamat might have been jealous of that and Ddraig thought Tiamat hates him.