Charles’ breakdown when he first tries to use Cerebro is actually terrifying when you think about how many people were screaming in agony and especially when you think about older Charles mentioned that if he concentrates too hard or is disrupted during the process he could seriously hurt or even kill them . Seeing how unstable young Charles was at this point, it isn’t hard to imagine that something really bad could’ve happened if he hadn’t taken off the helmet or gotten it together.
It’s my favourite thing about Charles, really, that the one thing standing between him and TOTAL ACTUAL WORLD DOMINATION is Charles himself.
Magneto, Shaw, Trask, whatever, they can posture and play super-villains all they want, but their methods, while effective, take time and visible effort. Charles can do it between the sips of his morning tea. It’s not that resistance would be futile, it’s that there would be no resistance, because you wouldn’t even know (a) there needs to be (b) it needs to be now. Because by the time you knew, you probably wouldn’t know and it would be too late.