Why wasn't Stranger Things nominated?

The Emmy calendar is tied to the traditional TV season, so the eligibility window ends in May. If they were to move the ceremony to align with the calendar year (like the Oscars, for example), the many network shows that still air from ~September to May would have their seasons split in half for Emmy purposes. Stranger Things will be eligible next year.

Yes, they missed the deadline. The deadline is May 31st, and Stranger Things didn't premiere until July. It will be eligible to be nominated next year, which I hope it does. The Emmy's go by the old television season when new series aired from September to May.

They weren't? That is surprising.

The villainy you teach me I will execute-and it shall go hard but I will better the instruction.