I think may people have a reasonable suspicion that he actually doesn't have any skills in fundraising, policy or business management at all, and that the only reason that he was appointed was becase he's trans-identifying.
If this man had had a long career in the charity sector and a demonstrable track record of success at the things that you mention, then you might have a point.
The only data I can find is that he has "worked with" three charities in the past. That's a really weak statement. "Working with" could mean as little as a weekly volunteer slot of a couple of hours, or even being the benficiary of support. I've "worked with" probably a dozen charities through my life, but it would politely be described as a stretch to say that qualifies me for the CEO position of this one.
Certainly if my "working with" three charities were in any stronger sense than something trivial and I were he then I would have found a way to say so - which charities, and which roles I fulfilled for them.
I can see why it might be helpful for a charity CEO to have some experience with or closely related to the charity's beneficial purpose, and I can also see that it's not mandatory. If a competent man had been appointed, this would be a very different discussion. It doesn't appear that the man who was appointed was in any way qualified, which leads one to the obvious answer to the question "why him?"