They had a month to level to 60 and gear up, most normal people aren’t into wasting a month to enter a tournament with practically no odds of getting anything. If you die in the tournament your character is done, so naturally the contestants are largely going to be people with some confidence and time to spare.
I hadn’t seen ESDF in FPS, I personally used to use it in WoW.
But mousewheel scroll is actually a great jump bind for when you precisely need to input the next jump action to time it with the end of the last. This is less an FPS thing and more a movement thing. Spacebar (or other buttons) will only work if you hit it at the precise time, while mousewheel is a lot more forgiving, since it is multiple inputs in quick succession, kind of like the rapid-fire macros. Like I suck at bhopping for example, but I could do some easy bhop sequences in cs 1.6 with scrollwheel, there is no way I would be able to with spacebar.