Rey was training with Luke on Ahch-To and after sensing the Balance and the light side of the force she noticed the dark.It offered her something that she wanted so she yielded and gave herself up to it.She didn’t even try to resist.
He’d seen this raw strength only once before, in Ben Solo.It didn’t scare him enough then, but it did now.
Photo Credits: Star Wars:The Last Jedi
Star Wars From Another Point Of View 