Of all the people that Irma could have taken Credence to, why was Mary Lou Barebone selected. Any checking would have revealed her anti Wizard stance and Snatcher family background..
..unless you wanted the child to repress their magical ability and grow an Obscurus..
There really only seems to be one person who'd be interesred in making that happen..
..but if that was true, why does Grindelwald know so little about the child until Credence reveals himself as the Obscurial? Surely he'd know at least the age and sex of the child.
As Irma delivered Credence to Mary Lou and only Credences Aunt was onboard with the baby, how does Mary Lou know Credences mother was a 'Wicked woman'? Was the information about her given to ensure the poor treatment of the child?