but why the fuck weren't women making this argument and demand of all politicians when the GRC was drafted and immediately beyond?
It's a boiling frog analogy. Good arguments were made against it at the time by a few dissenting politicians and very prophetic ones as it turns out. The landscape looked very different in 2004 to how it does now. The Tories were out of favour and not far out from the years they battled against gay people. The Blair government was still in its golden period and anyone vaguely liberal or to the left wasn't minded to listen to Ann Widecombe or Norman Tebbit.
Most people had never met what was known then as a transsexual. Cross dressing men (transvestites) unless they went the whole 9 yards with surgery etc. to become transsexual still did it behind closed doors in secret. The media hadn't yet rehabilitated and revered men who erotic cross to some kind of sainthood/ most marginalised status.
Social media didn't exist and pornography not as yet widely available. When the debates about the GRA occurred in 2003 the internet was still very much in its infancy, smart phones didn't exist and people still used dial up modems. The amount of time your average person spent on time was minimal compared to now.
Rolling news was still in its infancy too. Analysis and opinions on political issues, if you wanted them, still had to be sought mostly through the print media.
In 2004 I was in my 20's with two young children, a newborn and a job. I can barely remember the Act being passed. Like other women life kept me very busy and I wasn't paying attention.
Had I paid attention perhaps I would have thought it odd but not knowing this tiny cohort of people (mostly men)I might have assumed it was reasonable - based on how it was sold to the public at the time. In the aforementioned context of how society was at the time there wasn't a lot of reasons for the average, under informed person to imagine things would end up where they have.
Back to the boiling frog analogy it was only really about a decade ago that the water started getting uncomfortably warm for many women. A full 10 years after the GRA.
However I'm certain within that 10 years individual women will have felt the heat faster than others, for example, many lesbian women will have experienced problems long before I began to take notice. Transwidows are another group who will have felt ramifications earlier on than most.
It's possible that had society not changed very much from how it was in 2004 the GRA might not have become such a serious and widespread problem for women and girls. But society did change in those years, hugely and mostly down to big leaps in technology.
The notion of transgender/gender identity was invented, spread and taken mainstream via that technology with the help of lobby groups who grew stronger and more influential post GRA 2004. A massive and lucrative industry grew alongside it as well as the beginning of a new strand of politics that serves a number of agendas. That is where we find ourselves today.