Of course it was Jean who else was it going to be, I'm truly sorry if any Rachel/Emma/Quentin/etc fans assumed it'd be them.
Also, we should remember these are comics I'm not sure how long anyone expected Jean to remain in the role of the inexperienced telepath that initially ANXM thrived off, but even then she'd shown great strides in what she's capable of and with her potential it'd be stupid to still cast her as the young telepath needing guidance she's healed a number of minds in the last few years she's at this point simply the best choice.