IMO, the former fosters are not nice people, abusive to at least one child in their care, lie and are motivated by their image. JMO. Never met them, don’t know who they are.
But there is no evidence that is in the public domain that indicates to me they were responsible for his disappearance. There’s conjecture, opinions, possibilities but nothing solid. Circumstantial or otherwise.
I guess it’s possible there’s other circumstantial evidence they know that we don’t but if there is, it’s not enough to charge them.
They had a theory, could even be a good theory, could even be the theory that’s closest to the truth, but they have not be able to prove it. And judging by these latest comments they won’t be proving it anytime soon.