I honestly don't know how people fall for it.
I suspect that, in addition to those who see donating to the GLP as a good cause to support (particularly now Mermaids are a busted flush), there's a cohort of people who've bought the line that "trans rights are under attack" and are desperate for someone to "save them". This particularly applies to the sort of person you find on Transgender Reddit, convinced (sadly) that they're the potential victim of a genocide, "all GCs want us dead", so on and so forth.
Enter stage left: Jolyon, presenting as a knight in shining armour but actually just an idiot in tin foil.
(Whenever talk of GLP's finances come up, the image always comes to mind of Smaug sitting on his big pile of gold...)