I would be surprised if they were being paid.
Someone may have suggested ways in which it would be good for them to rejoin the crew.
An individual could be an "unpaid volunteer," hoping for some other type of gain which is important to him.
If I'm not mistaken, all of kerry's crew members supporting him received medals based on kerry's recommendations. If his credibility regarding medals is destroyed, their medals come under question as well.
If I were in their situation, that fact would provide me a very significant incentive to prop up his story, regardless of the truth or falsity of it.