I think it is important to note that the only way Mermaids was able to grow into the leviathan it did was because the key figure in the charity was a middle-aged mother.
Had the front face of Mermaids been anyone else, the strangeness of the message would have been noticed far earlier. No one would have accepted a middle-aged father arguing for this level of psychosexual medical and surgical intervention in children. He would have been shut down from the off. Likewise, anyone without children would not have worked, nor anyone younger.
It had to be a middle-aged mother with a trans child. That's the only figure with enough societal preconceptual armour to be able to slip past the glaringly obvious safe guarding and grooming issues.
And this is the problem for Mermaids. Because of the nature of the subject, it only works if the key voices are non-trans parents.