Why does mike leave katherin to mary susan again??what happened??

Dave wanted revenge so he took susan and mj to the place where the accident that killed his wife and daugther happened for killing susan so she called mike to rescue her and mj, he rescue her and they kissed each other and n the season 6 mike tell katherine that he never loved her and during all this time he was in Cinta with susan!!! Ps: the image shows the moment just after the accident that as supposed to kill mj!