I don't know what happened and neither do you. Fwiw, I was not in favor of him doing this, or a couple of the things he has done since.
That said, I don't think that just because he said what he did negates what he is doing now. He said, rightfully, that he knew this could jeopardize his career. There were a few different ways that could have happened. If, however, he found out that he was actually blackballed by the owners and/or league getting together, then it's possible that his feelings legitimately changed.
I have no idea if the owners colluded. I can easily understand how an individual owner would decide that Kaep at this point in his career was not worth all the crap that would invariably ensue with his signing. That's a legit stance and one I may even make myself. But that is not the same thing as being colluded against and blackballed. His complaint and lawsuit may be garbage and it may be legit.