Here is my potentially hot take:
Many of the founding and most active members here cook and do prep for a living, where efficiency is everything, bigger knives 240+ usually make the most sense (cutting 3 squashes at a time instead of 1-2 is faster, etc.). Most of the pros settled on 240s as the best balance of use in a small space and amble blade length. Cooks, with their boisterous nature and credentials, drove the norms on the forum leading to 240 gyuto being the "default" choice. More people bought them, praised their virtues, sold them, etc. perpetuating the 240 cycle we see here now.
Im a 270 guy personally... I just find that extra length very useable when doing tons of prep (more edge length to use when things start getting dull, ability for a more robust heel and laser tip, lots of flat spot, etc) and after a week of use I don't even notice the extra length anymore and honestly keep thinking about a 300+. I think Jon has mentioned before that pretty much every pro in Japan uses a 270 for gyuto and that the shorter lengths are an American thing. I honestly think the current zeitgeist of taller and taller knives relative the length is a product of people trying to gain back the benefits of length without exceeding the 240 arbitrary cut off. I'd much rather use a 270x50 than 240x60.
Finally, anything under 240 is a petty not a gyuto, 270+ for life!!!*
* yes I am compensating for my small small pipi