User blog comment:Observer Supreme/918 Review and Thoughts/@comment-29325824-20180920134308/@comment-29325824-20180920143547

Well, it's either that, or them somehow having been tangible ghosts this entire time (and I'm pretty sure we didn't cross over into Bleach). Or someone somehow managed to mass produce the Yomi Yomi no Mi and give it to those specific people.

Look, OP may be a setting of myriads of possibilities, but Occam's razor probably still applies there.