Snowdog, it could have been merely a relationship between adults, also sometimes characterized as an affair. I suppose that simply being in the dark about an intimate relationship between Kurt and Holly, and having it made known to you in open court for the first time would seem a betrayal. Be a betrayal, sure.
Looking back at Kurt’s hasty exit from his business, and the less than prudent financial losses he was willing to incur, coupled with the director’s framing of an earlier scene with Diane as anticipating Kurt wanted to divorce was the unspoken way of telling the viewers something was amiss.
Well.