People will do a lot to maintain close personal relationships. People pack this stuff away. Blaming the ship is easy, there's no personal baggage there to deal with. They can just offload all the guilt onto a faceless corporation. Honestly, this is the kind of thing family members will repress for years and years. Someday something might happen to trigger KW or AW to lash out at SA with a ton of repressed anger but for now they're doing what allows them to keep what's left of their family intact. Just an alternate reading IMO.
You assume these particular people WANT to look at the evidence/facts and WANT to alter their position. I still seriously doubt KW has watched the video. She's got her boogeyman in the form of RCCL. No need to look for another one where she doesn't really want to find one.
JMO, but this puts KW and AW on the same level as those who choose romantic partners over their children by turning a blind eye to abuse or molestation. As a parent, I believe your children's safety and well being should always be your top priority. In publicly defending the man who killed their daughter, they're saying he matters more to them than their own child did.