There are several plausible explanations, but not one which stands out. It has more in common with Ben Needham's case than with Claudia Lawrence's imo. The similarity is that both mothers have spent years claiming abduction. The difference is that the McCanns were able to mount a better campaign.
Apart from disappearing abroad I think there is far more in common with the abduction of the little six year old girl from her bath by a predatory paedophile/burglar who entered the ground floor flat where she was bathing, through an unlocked door.
He snatched the child from her bath and the only evidence of his existence was the mark of a footprint on the floor.
Her mother said:
"My little girl was in the bath in her own home within earshot of everyone else in the flat, the back door was shut and I'd only just left the bathroom to go to another room when she was snatched.
"It's every mother's nightmare to think your children aren't safe in their home. You wouldn't think you would have to lock all your doors this early in the evening to protect your children from anyone entering your home uninvited." https://www.theguardian.com/uk/2006/oct/20/ukcrimeThis horrific opportunistic crime was committed by a total stranger to the family.
At trial a life-long friend of the perpetrator gave evidence that he had said that he wanted to "do something" to a child when driving past two young children in the street.
The police had taken reports of the crime seriously right from the beginning and phone data indicated his presence in the area of the crime
Thankfully the little child was abandoned by her abductor and returned to her family.
If she had disappeared I think her family would have faced exactly the same type of mindless savagery meted out to Madeleine’s family because all the ingredients were there.
She was taken by a stranger and we only know what happened to her because she was found and was able to tell us; if she hadn’t her disappearance certainly would have been the stuff of conspiracy theorists piling on the grief to an already stricken family.
There are just those who cannot help themselves when a horrible 'opportunity' presents itself.