Another thought: transition is perhaps the only major event in parishioners' lives where the church doesn't currently have any involvement.
Hatches (through baptism), matches (weddings) and dispatches (funerals) are all church services. Divorces don't count because they aren't always recognised / approved of within the church community.
So I can see why the CofE was attracted initially to the idea of a service to celebrate / mark the transition, even if (as pp have said) it has no religious connection.
It's an interesting example of TRAs over-reaching, sympathetic naive people agreeing with their suggestions, then the general population going "wait, what??!"
If the CofE had published guidelines for clergy to adopt in dealing with trans parishioners (respect their choice of pronouns; ask them whether they want anything to be mentioned more generally in announcements or not type stuff) and a model prayer to use to welcome Bob Smith - who used to be Anne Smith - to the congregation, this probably wouldn't even have been noticed, never mind discussed on here and the national press.