There are a lot of Youtubers who are trans out there already but so what? If you make your content concise and accessible for people who's to say you won't thrive? If you network within the online trans community other people might well promote your content and you might become a popular channel. And you are right, it can help other people, including yourself to document the process.
My only concern if I were you would be if you were ready for people to see you on YouTube admitting your trans status. The community has the best and the worst of humanity to offer, and you might need to have a thick skin because people may well make negative response videos to your content, or leave negative comments (probably only likely if you do become well known). If it might put you in danger, if people might recognize you that would threaten you, or doxx you, you need to be careful. Once something is out there it can sometimes not be taken back.
If you don't think this will be a problem and could do regular content to satisfy a following, I can't see why you shouldn't go for it...
Some people just do it for themselves as well as a means to vent.