As far as I can make out, 18 year old Ranboo (pronouns he/him) is a minecraft youtuber/twitch streamer, with a massive LGBT following including many transmasc/non binary fans, who nicknamed him Genderman (I assume originally this is because Ranboo the character was half ghast, half enderman) and it became a joke - he said something about lots of people wanting to steal his gender cos of gender envy - him being so masculine. Said fans lapped it up/had a lot of banter about it. He is really just a nerdy, sweet young man making $$$$ from his bedroom, having played minecraft for 9 years, living his dream I guess...and confused as to how he won/was listed.
As am I...his demographic does not fit with the nominating for a Guardian poll at all, unless it was just the one, sole anonymous aussie rando. Or there are loads of transboys in adulation. He does the kind of schtick my son adores. Hint - he would not be filling in a poll.